Open Redirect and XSS in Web Filter warning page

Summary

An Improper Neutralization of Input During Web Page Generation and URL Redirection to Untrusted Site vulnerabilities [CWE-79, CWE-601] in FortiOS, FortiProxy and FortiSASE may allow an unauthenticated attacker to perform a reflected cross site scripting (XSS) or an open redirect attack via crafted HTTP requests.

Version Affected Solution
FortiOS 7.6 7.6.0 through 7.6.3 Upgrade to 7.6.4 or above
FortiOS 7.4 7.4.0 through 7.4.8 Upgrade to 7.4.9 or above
FortiOS 7.2 7.2 all versions Migrate to a fixed release
FortiOS 7.0 7.0 all versions Migrate to a fixed release
FortiOS 6.4 6.4 all versions Migrate to a fixed release
FortiProxy 7.6 7.6.0 through 7.6.3 Upgrade to 7.6.4 or above
FortiProxy 7.4 7.4 all versions Migrate to a fixed release
FortiProxy 7.2 7.2 all versions Migrate to a fixed release
FortiProxy 7.0 7.0 all versions Migrate to a fixed release
FortiSASE 25.2 25.2.a Fortinet remediated this issue in FortiSASE version 25.3.b and hence customers do not need to perform any action.
Follow the recommended upgrade path using our tool at: https://docs.fortinet.com/upgrade-tool

Acknowledgement

Fortinet is pleased to thank Yaniv Nizry from Sonar and Piotr Ryciak for reporting this vulnerability under responsible disclosure.

Timeline

2025-10-14: Initial publication