In this blog post, we discuss a recent finding where a team of security researchers, including @0xmagdy and @h_hussein11, successfully bypassed a Web Application Firewall (WAF) to escalate a Stored Cross-Site Scripting (XSS) vulnerability into a full account takeover. The key technique involved using the JavaScript property `window.location.href` as a payload to bypass certain WAFs that were intended to block such attacks.
Stored XSS occurs when malicious scripts are permanently stored on a target server, such as in a database, and then served to users. Traditionally, WAFs aim to detect and block suspicious script injections to prevent exploitation. However, this bypass demonstrates that some WAF implementations may fail to detect the use of `window.location.href` for redirections or other malicious actions, allowing attackers to execute harmful scripts effectively.
The consequence of this vulnerability is severe: from a simple Stored XSS, attackers can execute scripts that hijack user sessions, steal credentials, or perform actions on behalf of the victim, ultimately leading to a complete account takeover. The researchers acknowledged the importance of platforms like Intigriti for facilitating responsible disclosure and collaboration.
This finding highlights the need for continuous improvement in WAF capabilities and the importance of comprehensive testing against various bypass techniques. Security teams should review their filtering logic and consider advanced behavioral analysis to detect and block such sophisticated attacks.
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