Vulnerabilities > CVE-2021-31815 - Cleartext Transmission of Sensitive Information vulnerability in Google Google/Apple Exposure Notifications 20210427

Session sidejacking takes advantage of an unencrypted communication channel between a victim and target system. The attacker sniffs traffic on a network looking for session tokens in unencrypted traffic. Once a session token is captured, the attacker performs malicious actions by using the stolen token with the targeted application to impersonate the victim. This attack is a specific method of session hijacking, which is exploiting a valid session token to gain unauthorized access to a target system or information. Other methods to perform a session hijacking are session fixation, cross-site scripting, or compromising a user or server machine and stealing the session token.

An attacker engages in probing and exploration activity to identify constituents and properties of the target. Footprinting is a general term to describe a variety of information gathering techniques, often used by attackers in preparation for some attack. It consists of using tools to learn as much as possible about the composition, configuration, and security mechanisms of the targeted application, system or network. Information that might be collected during a footprinting effort could include open ports, applications and their versions, network topology, and similar information. While footprinting is not intended to be damaging (although certain activities, such as network scans, can sometimes cause disruptions to vulnerable applications inadvertently) it may often pave the way for more damaging attacks.

An attacker hosts an event within an application framework and then monitors the data exchanged during the course of the event for the purpose of harvesting any important data leaked during the transactions. One example could be harvesting lists of usernames or userIDs for the purpose of sending spam messages to those users. One example of this type of attack involves the attacker creating an event within the sub-application. Assume the attacker hosts a "virtual sale" of rare items. As other users enter the event, the attacker records via MITM proxy the user_ids and usernames of everyone who attends. The attacker would then be able to spam those users within the application using an automated script.

An attacker exploits the underlying complexity of a data structure that allows for both signed and unsigned content, to cause unsigned data to be processed as though it were signed data.

Attackers can capture application code bound for the client and can use it, as-is or through reverse-engineering, to glean sensitive information or exploit the trust relationship between the client and server. Such code may belong to a dynamic update to the client, a patch being applied to a client component or any such interaction where the client is authorized to communicate with the server.