MantisBT is Vulnerable to Stored XSS in Custom Field Textarea Values

Improper escaping of a textarea custom field's contents in the Update Issue page (bug_update_page.php) allows an attacker to inject HTML and, if CSP settings permit, execute arbitrary JavaScript when the page is loaded.

Impact

Session theft leading to admin account takeover, full project data access.

• Precondition: A textarea-type custom field must be configured for the project
• Attacker: Authenticated user with bug report permission (low privilege)
• Victim: Any user viewing the bug edit form, including administrators

Patches

• 5fec0f448b7a7d7d539a6adb6dccceac4e4e4ab7

Workarounds

The default Content-Security Policy will block script execution.

References

• https://mantisbt.org/bugs/view.php?id=37003
• This is related to CVE-2024-34081.

Credits

Thanks to the following security researchers for independently discovering and responsibly reporting the issue, and providing a patch to fix it.

• Thanks to Nozomu Sasaki (Paul) (@morimori-dev)
• Tristan Madani (@TristanInSec) from Talence Security