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](https://github.com/advisories/GHSA-wgx7-jp56-65mq). ### 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
describes (1)
Related CVEs.
| ID | severity | exploitable | ||
|---|---|---|---|---|
| CVE-2026-39960US | — | — | ||
Mantis Bug Tracker (MantisBT) is an open source issue tracker. Versions 2.28.1 and below contain flawed logic that causes improper escaping of a textarea custom field's contents in… | ||||
references
External citations — patches, advisories, analysis.
- https://github.com/mantisbt/mantisbtPACKAGE
- https://github.com/mantisbt/mantisbt/commit/5fec0f448b7a7d7d539a6adb6dccceac4e4e4ab7WEB
- https://github.com/mantisbt/mantisbt/security/advisories/GHSA-qj6w-v29q-4rgxWEB
- https://mantisbt.org/bugs/view.php?id=37003WEB
- https://nvd.nist.gov/vuln/detail/CVE-2026-39960ADVISORY
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