Vulnerabilities > CVE-2015-8936 - Cross-site Scripting vulnerability in Squidguard

047910
CVSS 6.1 - MEDIUM
Attack vector
NETWORK
Attack complexity
LOW
Privileges required
NONE
Confidentiality impact
LOW
Integrity impact
LOW
Availability impact
NONE
network
low complexity
squidguard
CWE-79
nessus
NVD
Published: 2017-02-09
Updated: 2024-11-21

Summary

Cross-site scripting (XSS) vulnerability in squidGuard.cgi in squidGuard before 1.5 allows remote attackers to inject arbitrary web script or HTML via a blocked site link.

Vulnerable Configurations

Part Description Count
Application
Squidguard
1

Common Weakness Enumeration (CWE)

Common Attack Pattern Enumeration and Classification (CAPEC)

  • Cross Site Scripting through Log Files
    An attacker may leverage a system weakness where logs are susceptible to log injection to insert scripts into the system's logs. If these logs are later viewed by an administrator through a thin administrative interface and the log data is not properly HTML encoded before being written to the page, the attackers' scripts stored in the log will be executed in the administrative interface with potentially serious consequences. This attack pattern is really a combination of two other attack patterns: log injection and stored cross site scripting.
  • Embedding Scripts in Non-Script Elements
    This attack is a form of Cross-Site Scripting (XSS) where malicious scripts are embedded in elements that are not expected to host scripts such as image tags (<img>), comments in XML documents (< !-CDATA->), etc. These tags may not be subject to the same input validation, output validation, and other content filtering and checking routines, so this can create an opportunity for an attacker to tunnel through the application's elements and launch a XSS attack through other elements. As with all remote attacks, it is important to differentiate the ability to launch an attack (such as probing an internal network for unpatched servers) and the ability of the remote attacker to collect and interpret the output of said attack.
  • Embedding Scripts within Scripts
    An attack of this type exploits a programs' vulnerabilities that are brought on by allowing remote hosts to execute scripts. The attacker leverages this capability to execute scripts to execute his/her own script by embedding it within other scripts that the target software is likely to execute. The attacker must have the ability to inject script into script that is likely to be executed. If this is done, then the attacker can potentially launch a variety of probes and attacks against the web server's local environment, in many cases the so-called DMZ, back end resources the web server can communicate with, and other hosts. With the proliferation of intermediaries, such as Web App Firewalls, network devices, and even printers having JVMs and Web servers, there are many locales where an attacker can inject malicious scripts. Since this attack pattern defines scripts within scripts, there are likely privileges to execute said attack on the host. Of course, these attacks are not solely limited to the server side, client side scripts like Ajax and client side JavaScript can contain malicious scripts as well. In general all that is required is for there to be sufficient privileges to execute a script, but not protected against writing.
  • Cross-Site Scripting in Error Pages
    An attacker distributes a link (or possibly some other query structure) with a request to a third party web server that is malformed and also contains a block of exploit code in order to have the exploit become live code in the resulting error page. When the third party web server receives the crafted request and notes the error it then creates an error message that echoes the malformed message, including the exploit. Doing this converts the exploit portion of the message into to valid language elements that are executed by the viewing browser. When a victim executes the query provided by the attacker the infected error message error message is returned including the exploit code which then runs in the victim's browser. XSS can result in execution of code as well as data leakage (e.g. session cookies can be sent to the attacker). This type of attack is especially dangerous since the exploit appears to come from the third party web server, who the victim may trust and hence be more vulnerable to deception.
  • Cross-Site Scripting Using Alternate Syntax
    The attacker uses alternate forms of keywords or commands that result in the same action as the primary form but which may not be caught by filters. For example, many keywords are processed in a case insensitive manner. If the site's web filtering algorithm does not convert all tags into a consistent case before the comparison with forbidden keywords it is possible to bypass filters (e.g., incomplete black lists) by using an alternate case structure. For example, the "script" tag using the alternate forms of "Script" or "ScRiPt" may bypass filters where "script" is the only form tested. Other variants using different syntax representations are also possible as well as using pollution meta-characters or entities that are eventually ignored by the rendering engine. The attack can result in the execution of otherwise prohibited functionality.

Nessus

  • NASL familySuSE Local Security Checks
    NASL idSUSE_SU-2016-2510-1.NASL
    descriptionsquidGuard was updated to fix one security issue. This security issue was fixed : - CVE-2015-8936: Reflected cross-site scripting vulnerability because of insufficient escaping (bsc#985612). Note that Tenable Network Security has extracted the preceding description block directly from the SUSE security advisory. Tenable has attempted to automatically clean and format it as much as possible without introducing additional issues.
    last seen2020-06-01
    modified2020-06-02
    plugin id94040
    published2016-10-13
    reporterThis script is Copyright (C) 2016-2019 and is owned by Tenable, Inc. or an Affiliate thereof.
    sourcehttps://www.tenable.com/plugins/nessus/94040
    titleSUSE SLES11 Security Update : squidGuard (SUSE-SU-2016:2510-1)
    code
    #
# (C) Tenable Network Security, Inc.
#
# The descriptive text and package checks in this plugin were
# extracted from SUSE update advisory SUSE-SU-2016:2510-1.
# The text itself is copyright (C) SUSE.
#

include("compat.inc");

if (description)
{
  script_id(94040);
  script_version("2.6");
  script_cvs_date("Date: 2019/09/11 11:22:14");

  script_cve_id("CVE-2015-8936");

  script_name(english:"SUSE SLES11 Security Update : squidGuard (SUSE-SU-2016:2510-1)");
  script_summary(english:"Checks rpm output for the updated packages.");

  script_set_attribute(
    attribute:"synopsis", 
    value:"The remote SUSE host is missing one or more security updates."
  );
  script_set_attribute(
    attribute:"description", 
    value:
"squidGuard was updated to fix one security issue. This security issue
was fixed :

  - CVE-2015-8936: Reflected cross-site scripting
    vulnerability because of insufficient escaping
    (bsc#985612).

Note that Tenable Network Security has extracted the preceding
description block directly from the SUSE security advisory. Tenable
has attempted to automatically clean and format it as much as possible
without introducing additional issues."
  );
  script_set_attribute(
    attribute:"see_also",
    value:"https://bugzilla.suse.com/show_bug.cgi?id=985612"
  );
  script_set_attribute(
    attribute:"see_also",
    value:"https://www.suse.com/security/cve/CVE-2015-8936/"
  );
  # https://www.suse.com/support/update/announcement/2016/suse-su-20162510-1/
  script_set_attribute(
    attribute:"see_also",
    value:"http://www.nessus.org/u?955dc0b7"
  );
  script_set_attribute(
    attribute:"solution", 
    value:
"To install this SUSE Security Update use YaST online_update.
Alternatively you can run the command listed for your product :

SUSE Linux Enterprise Server 11-SP4:zypper in -t patch
slessp4-squidGuard-12783=1

SUSE Linux Enterprise Debuginfo 11-SP4:zypper in -t patch
dbgsp4-squidGuard-12783=1

To bring your system up-to-date, use 'zypper patch'."
  );
  script_set_cvss_base_vector("CVSS2#AV:N/AC:M/Au:N/C:N/I:P/A:N");
  script_set_cvss_temporal_vector("CVSS2#E:U/RL:OF/RC:C");
  script_set_cvss3_base_vector("CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N");
  script_set_cvss3_temporal_vector("CVSS:3.0/E:U/RL:O/RC:C");
  script_set_attribute(attribute:"exploitability_ease", value:"No known exploits are available");
  script_set_attribute(attribute:"exploit_available", value:"false");

  script_set_attribute(attribute:"plugin_type", value:"local");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:novell:suse_linux:squidGuard");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:novell:suse_linux:squidGuard-doc");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:novell:suse_linux:11");

  script_set_attribute(attribute:"vuln_publication_date", value:"2017/02/09");
  script_set_attribute(attribute:"patch_publication_date", value:"2016/10/12");
  script_set_attribute(attribute:"plugin_publication_date", value:"2016/10/13");
  script_set_attribute(attribute:"generated_plugin", value:"current");
  script_end_attributes();

  script_category(ACT_GATHER_INFO);
  script_copyright(english:"This script is Copyright (C) 2016-2019 and is owned by Tenable, Inc. or an Affiliate thereof.");
  script_family(english:"SuSE Local Security Checks");

  script_dependencies("ssh_get_info.nasl");
  script_require_keys("Host/local_checks_enabled", "Host/cpu", "Host/SuSE/release", "Host/SuSE/rpm-list");

  exit(0);
}


include("audit.inc");
include("global_settings.inc");
include("rpm.inc");


if (!get_kb_item("Host/local_checks_enabled")) audit(AUDIT_LOCAL_CHECKS_NOT_ENABLED);
release = get_kb_item("Host/SuSE/release");
if (isnull(release) || release !~ "^(SLED|SLES)") audit(AUDIT_OS_NOT, "SUSE");
os_ver = pregmatch(pattern: "^(SLE(S|D)\d+)", string:release);
if (isnull(os_ver)) audit(AUDIT_UNKNOWN_APP_VER, "SUSE");
os_ver = os_ver[1];
if (! preg(pattern:"^(SLES11)$", string:os_ver)) audit(AUDIT_OS_NOT, "SUSE SLES11", "SUSE " + os_ver);

if (!get_kb_item("Host/SuSE/rpm-list")) audit(AUDIT_PACKAGE_LIST_MISSING);

cpu = get_kb_item("Host/cpu");
if (isnull(cpu)) audit(AUDIT_UNKNOWN_ARCH);
if (cpu !~ "^i[3-6]86$" && "x86_64" >!< cpu && "s390x" >!< cpu) audit(AUDIT_LOCAL_CHECKS_NOT_IMPLEMENTED, "SUSE " + os_ver, cpu);

sp = get_kb_item("Host/SuSE/patchlevel");
if (isnull(sp)) sp = "0";
if (os_ver == "SLES11" && (! preg(pattern:"^(4)$", string:sp))) audit(AUDIT_OS_NOT, "SLES11 SP4", os_ver + " SP" + sp);


flag = 0;
if (rpm_check(release:"SLES11", sp:"4", reference:"squidGuard-1.4-13.10.1")) flag++;
if (rpm_check(release:"SLES11", sp:"4", reference:"squidGuard-doc-1.4-13.10.1")) flag++;


if (flag)
{
  set_kb_item(name:'www/0/XSS', value:TRUE);
  if (report_verbosity > 0) security_warning(port:0, extra:rpm_report_get());
  else security_warning(0);
  exit(0);
}
else
{
  tested = pkg_tests_get();
  if (tested) audit(AUDIT_PACKAGE_NOT_AFFECTED, tested);
  else audit(AUDIT_PACKAGE_NOT_INSTALLED, "squidGuard");
}
  • NASL familySuSE Local Security Checks
    NASL idOPENSUSE-2016-1210.NASL
    descriptionsquidGuard was updated to fix one security issue. This security issue was fixed : - CVE-2015-8936: Reflected cross site scripting vulnerability because of insufficient escaping (bsc#985612). This update was imported from the SUSE:SLE-12:Update update project.
    last seen2020-06-05
    modified2016-10-24
    plugin id94218
    published2016-10-24
    reporterThis script is Copyright (C) 2016-2020 Tenable Network Security, Inc.
    sourcehttps://www.tenable.com/plugins/nessus/94218
    titleopenSUSE Security Update : squidGuard (openSUSE-2016-1210)
    code
    #%NASL_MIN_LEVEL 80502
#
# (C) Tenable Network Security, Inc.
#
# The descriptive text and package checks in this plugin were
# extracted from openSUSE Security Update openSUSE-2016-1210.
#
# The text description of this plugin is (C) SUSE LLC.
#

include("compat.inc");

if (description)
{
  script_id(94218);
  script_version("2.4");
  script_set_attribute(attribute:"plugin_modification_date", value:"2020/06/04");

  script_cve_id("CVE-2015-8936");

  script_name(english:"openSUSE Security Update : squidGuard (openSUSE-2016-1210)");
  script_summary(english:"Check for the openSUSE-2016-1210 patch");

  script_set_attribute(
    attribute:"synopsis", 
    value:"The remote openSUSE host is missing a security update."
  );
  script_set_attribute(
    attribute:"description", 
    value:
"squidGuard was updated to fix one security issue.

This security issue was fixed :

  - CVE-2015-8936: Reflected cross site scripting
    vulnerability because of insufficient escaping
    (bsc#985612).

This update was imported from the SUSE:SLE-12:Update update project."
  );
  script_set_attribute(
    attribute:"see_also",
    value:"https://bugzilla.opensuse.org/show_bug.cgi?id=985612"
  );
  script_set_attribute(
    attribute:"solution", 
    value:"Update the affected squidGuard packages."
  );
  script_set_cvss_base_vector("CVSS2#AV:N/AC:M/Au:N/C:N/I:P/A:N");
  script_set_cvss3_base_vector("CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N");

  script_set_attribute(attribute:"plugin_type", value:"local");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:novell:opensuse:squidGuard");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:novell:opensuse:squidGuard-debuginfo");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:novell:opensuse:squidGuard-debugsource");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:novell:opensuse:42.1");

  script_set_attribute(attribute:"patch_publication_date", value:"2016/10/21");
  script_set_attribute(attribute:"plugin_publication_date", value:"2016/10/24");
  script_end_attributes();

  script_category(ACT_GATHER_INFO);
  script_copyright(english:"This script is Copyright (C) 2016-2020 Tenable Network Security, Inc.");
  script_family(english:"SuSE Local Security Checks");

  script_dependencies("ssh_get_info.nasl");
  script_require_keys("Host/local_checks_enabled", "Host/SuSE/release", "Host/SuSE/rpm-list", "Host/cpu");

  exit(0);
}


include("audit.inc");
include("global_settings.inc");
include("rpm.inc");

if (!get_kb_item("Host/local_checks_enabled")) audit(AUDIT_LOCAL_CHECKS_NOT_ENABLED);
release = get_kb_item("Host/SuSE/release");
if (isnull(release) || release =~ "^(SLED|SLES)") audit(AUDIT_OS_NOT, "openSUSE");
if (release !~ "^(SUSE42\.1)$") audit(AUDIT_OS_RELEASE_NOT, "openSUSE", "42.1", release);
if (!get_kb_item("Host/SuSE/rpm-list")) audit(AUDIT_PACKAGE_LIST_MISSING);

ourarch = get_kb_item("Host/cpu");
if (!ourarch) audit(AUDIT_UNKNOWN_ARCH);
if (ourarch !~ "^(i586|i686|x86_64)$") audit(AUDIT_ARCH_NOT, "i586 / i686 / x86_64", ourarch);

flag = 0;

if ( rpm_check(release:"SUSE42.1", reference:"squidGuard-1.4-3.1") ) flag++;
if ( rpm_check(release:"SUSE42.1", reference:"squidGuard-debuginfo-1.4-3.1") ) flag++;
if ( rpm_check(release:"SUSE42.1", reference:"squidGuard-debugsource-1.4-3.1") ) flag++;

if (flag)
{
  if (report_verbosity > 0) security_warning(port:0, extra:rpm_report_get());
  else security_warning(0);
  exit(0);
}
else
{
  tested = pkg_tests_get();
  if (tested) audit(AUDIT_PACKAGE_NOT_AFFECTED, tested);
  else audit(AUDIT_PACKAGE_NOT_INSTALLED, "squidGuard / squidGuard-debuginfo / squidGuard-debugsource");
}
  • NASL familyFedora Local Security Checks
    NASL idFEDORA_2016-FBB5A65729.NASL
    descriptionUnit file fix. ---- http://www.squidguard.org/Downloads/Patches/1.4/Readme.Patch-20150201 Note that Tenable Network Security has extracted the preceding description block directly from the Fedora update system website. Tenable has attempted to automatically clean and format it as much as possible without introducing additional issues.
    last seen2020-06-05
    modified2016-07-15
    plugin id92307
    published2016-07-15
    reporterThis script is Copyright (C) 2016-2020 and is owned by Tenable, Inc. or an Affiliate thereof.
    sourcehttps://www.tenable.com/plugins/nessus/92307
    titleFedora 22 : squidGuard (2016-fbb5a65729)
    code
    #%NASL_MIN_LEVEL 80502
#
# (C) Tenable Network Security, Inc.
#
# The descriptive text and package checks in this plugin were  
# extracted from Fedora Security Advisory FEDORA-2016-fbb5a65729.
#

include("compat.inc");

if (description)
{
  script_id(92307);
  script_version("2.5");
  script_set_attribute(attribute:"plugin_modification_date", value:"2020/06/04");

  script_cve_id("CVE-2015-8936");
  script_xref(name:"FEDORA", value:"2016-fbb5a65729");

  script_name(english:"Fedora 22 : squidGuard (2016-fbb5a65729)");
  script_summary(english:"Checks rpm output for the updated package.");

  script_set_attribute(
    attribute:"synopsis", 
    value:"The remote Fedora host is missing a security update."
  );
  script_set_attribute(
    attribute:"description", 
    value:
"Unit file fix.

----

http://www.squidguard.org/Downloads/Patches/1.4/Readme.Patch-20150201

Note that Tenable Network Security has extracted the preceding
description block directly from the Fedora update system website.
Tenable has attempted to automatically clean and format it as much as
possible without introducing additional issues."
  );
  script_set_attribute(
    attribute:"see_also",
    value:"http://www.squidguard.org/Downloads/Patches/1.4/Readme.Patch-20150201"
  );
  script_set_attribute(
    attribute:"see_also",
    value:"https://bodhi.fedoraproject.org/updates/FEDORA-2016-fbb5a65729"
  );
  script_set_attribute(
    attribute:"solution", 
    value:"Update the affected squidGuard package."
  );
  script_set_cvss_base_vector("CVSS2#AV:N/AC:M/Au:N/C:N/I:P/A:N");
  script_set_cvss3_base_vector("CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N");

  script_set_attribute(attribute:"plugin_type", value:"local");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:fedoraproject:fedora:squidGuard");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:fedoraproject:fedora:22");

  script_set_attribute(attribute:"vuln_publication_date", value:"2017/02/09");
  script_set_attribute(attribute:"patch_publication_date", value:"2016/06/30");
  script_set_attribute(attribute:"plugin_publication_date", value:"2016/07/15");
  script_set_attribute(attribute:"generated_plugin", value:"current");
  script_end_attributes();

  script_category(ACT_GATHER_INFO);
  script_copyright(english:"This script is Copyright (C) 2016-2020 and is owned by Tenable, Inc. or an Affiliate thereof.");
  script_family(english:"Fedora Local Security Checks");

  script_dependencies("ssh_get_info.nasl");
  script_require_keys("Host/local_checks_enabled", "Host/RedHat/release", "Host/RedHat/rpm-list");

  exit(0);
}


include("audit.inc");
include("global_settings.inc");
include("rpm.inc");


if (!get_kb_item("Host/local_checks_enabled")) audit(AUDIT_LOCAL_CHECKS_NOT_ENABLED);
release = get_kb_item("Host/RedHat/release");
if (isnull(release) || "Fedora" >!< release) audit(AUDIT_OS_NOT, "Fedora");
os_ver = pregmatch(pattern: "Fedora.*release ([0-9]+)", string:release);
if (isnull(os_ver)) audit(AUDIT_UNKNOWN_APP_VER, "Fedora");
os_ver = os_ver[1];
if (! preg(pattern:"^22([^0-9]|$)", string:os_ver)) audit(AUDIT_OS_NOT, "Fedora 22", "Fedora " + os_ver);

if (!get_kb_item("Host/RedHat/rpm-list")) audit(AUDIT_PACKAGE_LIST_MISSING);


cpu = get_kb_item("Host/cpu");
if (isnull(cpu)) audit(AUDIT_UNKNOWN_ARCH);
if ("x86_64" >!< cpu && cpu !~ "^i[3-6]86$") audit(AUDIT_LOCAL_CHECKS_NOT_IMPLEMENTED, "Fedora", cpu);


flag = 0;
if (rpm_check(release:"FC22", reference:"squidGuard-1.4-26.fc22")) flag++;


if (flag)
{
  security_report_v4(
    port       : 0,
    severity   : SECURITY_WARNING,
    extra      : rpm_report_get()
  );
  exit(0);
}
else
{
  tested = pkg_tests_get();
  if (tested) audit(AUDIT_PACKAGE_NOT_AFFECTED, tested);
  else audit(AUDIT_PACKAGE_NOT_INSTALLED, "squidGuard");
}
  • NASL familySuSE Local Security Checks
    NASL idSUSE_SU-2017-1411-1.NASL
    descriptionsquidGuard was updated to fix one security issue : - CVE-2015-8936: Reflected cross-site scripting vulnerability because of insufficient escaping (bsc#985612). Note that Tenable Network Security has extracted the preceding description block directly from the SUSE security advisory. Tenable has attempted to automatically clean and format it as much as possible without introducing additional issues.
    last seen2020-06-01
    modified2020-06-02
    plugin id100459
    published2017-05-26
    reporterThis script is Copyright (C) 2017-2019 and is owned by Tenable, Inc. or an Affiliate thereof.
    sourcehttps://www.tenable.com/plugins/nessus/100459
    titleSUSE SLES12 Security Update : squidGuard (SUSE-SU-2017:1411-1)
  • NASL familyFedora Local Security Checks
    NASL idFEDORA_2016-8B19472A3C.NASL
    descriptionUnit file fix. ---- http://www.squidguard.org/Downloads/Patches/1.4/Readme.Patch-20150201 Note that Tenable Network Security has extracted the preceding description block directly from the Fedora update system website. Tenable has attempted to automatically clean and format it as much as possible without introducing additional issues.
    last seen2020-06-05
    modified2016-07-15
    plugin id92266
    published2016-07-15
    reporterThis script is Copyright (C) 2016-2020 and is owned by Tenable, Inc. or an Affiliate thereof.
    sourcehttps://www.tenable.com/plugins/nessus/92266
    titleFedora 24 : squidGuard (2016-8b19472a3c)
  • NASL familyDebian Local Security Checks
    NASL idDEBIAN_DLA-524.NASL
    descriptionIt was discovered that there was a reflected cross-site scripting vulnerability in squidguard, a filter and redirector plugin for Squid. For Debian 7
    last seen2020-03-17
    modified2016-06-23
    plugin id91771
    published2016-06-23
    reporterThis script is Copyright (C) 2016-2020 Tenable Network Security, Inc.
    sourcehttps://www.tenable.com/plugins/nessus/91771
    titleDebian DLA-524-1 : squidguard security update
  • NASL familyFedora Local Security Checks
    NASL idFEDORA_2016-F8A01AA629.NASL
    descriptionUnit file fix. ---- http://www.squidguard.org/Downloads/Patches/1.4/Readme.Patch-20150201 Note that Tenable Network Security has extracted the preceding description block directly from the Fedora update system website. Tenable has attempted to automatically clean and format it as much as possible without introducing additional issues.
    last seen2020-06-05
    modified2016-07-15
    plugin id92305
    published2016-07-15
    reporterThis script is Copyright (C) 2016-2020 and is owned by Tenable, Inc. or an Affiliate thereof.
    sourcehttps://www.tenable.com/plugins/nessus/92305
    titleFedora 23 : squidGuard (2016-f8a01aa629)
  • NASL familySuSE Local Security Checks
    NASL idSUSE_SU-2016-2511-1.NASL
    descriptionsquidGuard was updated to fix one security issue. This security issue was fixed : - CVE-2015-8936: Reflected cross-site scripting vulnerability because of insufficient escaping (bsc#985612). Note that Tenable Network Security has extracted the preceding description block directly from the SUSE security advisory. Tenable has attempted to automatically clean and format it as much as possible without introducing additional issues.
    last seen2020-06-01
    modified2020-06-02
    plugin id94041
    published2016-10-13
    reporterThis script is Copyright (C) 2016-2019 and is owned by Tenable, Inc. or an Affiliate thereof.
    sourcehttps://www.tenable.com/plugins/nessus/94041
    titleSUSE SLES12 Security Update : squidGuard (SUSE-SU-2016:2511-1)

References