Vulnerabilities > CVE-2017-0928 - External Control of Critical State Data vulnerability in Theguardian Html-Janitor 2.0.2

An attacker examines an available client application for the presence of sensitive information. This information may be stored in configuration files, embedded within the application itself, or stored in other ways. Sensitive information may include long-term keys, passwords, credit card or financial information, and other private material that the client uses in its interactions with the server. While servers are (hopefully) protected with professional security administrators, most users may be less skilled at protecting their clients. As a result, the user client may represent a weak link that an attacker can exploit. If an attacker can gain access to a client installation, they may be able to detect and lift sensitive information that could be used directly (such as financial information), or allow the attacker to subvert future communication between the client and the server. In some cases, it may not even be necessary to gain access to another user's installation - if all instances of the client software are embedded with the same sensitive information (for example, long term keys for communication with the server) then the attacker must simply find a way to gain their own copy of the client in order to perform this attack.

Attacks on session IDs and resource IDs take advantage of the fact that some software accepts user input without verifying its authenticity. For example, a message queuing system that allows service requesters to post messages to its queue through an open channel (such as anonymous FTP), authorization is done through checking group or role membership contained in the posted message. However, there is no proof that the message itself, the information in the message (such group or role membership), or indeed the process that wrote the message to the queue are authentic and authorized to do so. Many server side processes are vulnerable to these attacks because the server to server communications have not been analyzed from a security perspective or the processes "trust" other systems because they are behind a firewall. In a similar way servers that use easy to guess or spoofable schemes for representing digital identity can also be vulnerable. Such systems frequently use schemes without cryptography and digital signatures (or with broken cryptography). Session IDs may be guessed due to insufficient randomness, poor protection (passed in the clear), lack of integrity (unsigned), or improperly correlation with access control policy enforcement points. Exposed configuration and properties files that contain system passwords, database connection strings, and such may also give an attacker an edge to identify these identifiers. The net result is that spoofing and impersonation is possible leading to an attacker's ability to break authentication, authorization, and audit controls on the system.

This attack relies on the use of HTTP Cookies to store credentials, state information and other critical data on client systems. The first form of this attack involves accessing HTTP Cookies to mine for potentially sensitive data contained therein. The second form of this attack involves intercepting this data as it is transmitted from client to server. This intercepted information is then used by the attacker to impersonate the remote user/session. The third form is when the cookie's content is modified by the attacker before it is sent back to the server. Here the attacker seeks to convince the target server to operate on this falsified information.