Google Tag Manager Script Content-Security-Policy Bypass Scanner

Google Tag Manager is a tag management system used by marketing teams to quickly and easily update tags and code snippets intended for traffic analysis and marketing optimization. This tool is largely employed by companies to simplify tag integration, without involving webmasters in the process. It facilitates better campaign tracking and reduces the dependency on direct code deployment. With its real-time debugging console, it enables testing while ensuring tags are properly configured and triggers fire properly. Google Tag Manager connects to other Google services and third-party applications to streamline marketing efforts. Its extensive use across various industries signifies its importance in modern digital marketing strategies.

The scanner identifies a Cross-Site Scripting (XSS) vulnerability in Google Tag Manager related to Content-Security-Policy Bypass. XSS vulnerabilities occur when attackers inject malicious scripts into web pages viewed by other users, potentially leading to unauthorized actions on behalf of these users. Through this scanner, security professionals can detect if the application’s CSP (Content Security Policy) configurations can be bypassed. Successfully identifying this issue is crucial as it could allow attackers to run arbitrary code in a user's browser. The scanner aids in discovering such vulnerabilities to protect web applications from XSS attacks. Detecting these vulnerabilities contributes to securing sensitive data and maintaining the trust of application users.

The scanner checks for CSP bypass in the Google Tag Manager by attempting to inject a script through the tag manager interface. It uses header response analysis to check if the CSP is detectable and validates if an alert can be triggered, indicating an XSS vulnerability. By simulating a CSP bypass attempt, the scanner confirms the presence of an exploitable security misconfiguration. The vulnerable parameter in this scenario involves the misuse of predefined scripts that can inject unauthorized content. The technical assessment involves analyzing the Content-Security-Policy header and associated behaviors that expose vulnerabilities. Through fuzzing and predefined payloads, the scanner evaluates the efficacy of the web application's CSP against intentional misuse.

If exploited, this vulnerability could allow attackers to execute scripts in the context of affected users' browsers, potentially leading to data theft, user impersonation, and unauthorized actions within the application. Malicious actors could exploit this to phish for credentials, capture keystrokes, or perform actions within a legitimate user's session. Successful CSP bypass attacks can have significant security implications, especially in environments storing or handling sensitive user data. Unaddressed vulnerabilities may also lead to compromised user experiences and damage to the organization's reputation. Therefore, identifying and mitigating such vulnerabilities is critical for maintaining cybersecurity.

REFERENCES

• https://github.com/renniepak/CSPBypass/blob/main/data.tsv