This indicates an attack attempt against a cross-site scripting (XSS) vulnerability in Mozilla Firefox.
The vulnerability is caused by an error when the HTML parser handles a specially crafted web page. It allows a remote attacker to bypass cross-site scripting (XSS) protection mechanisms and cause XSS attacks.
Mozilla Firefox 3.0.1 and previous versions
Mozilla Firefox 126.96.36.199 and previous versions
Security Bypass: Remote attackers can bypass security checking of vulnerable systems.
Update to the latest versions: