{"id":"CVE-2026-39960","aliases":["GHSA-qj6w-v29q-4rgx"],"url":"https://o3.security/vulnerability/CVE-2026-39960","summary":"MantisBT is Vulnerable to Stored XSS through Custom Field Textarea Values","details":"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.\n\n### Impact\nSession theft leading to admin account takeover, full project data access.\n\n- Precondition: A textarea-type custom field must be configured for the project\n- Attacker: Authenticated user with bug report permission (low privilege)\n- Victim: Any user viewing the bug edit form, including administrators\n\n### Patches\n- 5fec0f448b7a7d7d539a6adb6dccceac4e4e4ab7\n\n### Workarounds\nThe default Content-Security Policy will block script execution.\n\n### References\n- https://mantisbt.org/bugs/view.php?id=37003\n- This is related to [CVE-2024-34081](https://github.com/advisories/GHSA-wgx7-jp56-65mq).\n\n### Credits\nThanks to the following security researchers for independently discovering and responsibly reporting the issue, and providing a patch to fix it.\n- Thanks to Nozomu Sasaki (Paul) (@morimori-dev)\n- Tristan Madani (@TristanInSec) from Talence Security","published":"2026-05-20T21:11:02.341Z","modified":"2026-08-12T03:51:43.953374191Z","cvss":{"score":5.4,"severity":"MEDIUM","vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N"},"epss":{"score":0.0023,"percentile":0.14054,"asOf":"2026-08-15"},"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"Packagist","name":"mantisbt/mantisbt","fixedVersion":"2.28.2"}],"fix":{"url":"https://github.com/mantisbt/mantisbt/commit/5fec0f448b7a7d7d539a6adb6dccceac4e4e4ab7","label":"mantisbt/mantisbt@5fec0f4"},"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/39xxx/CVE-2026-39960.json"},{"type":"ADVISORY","url":"https://github.com/mantisbt/mantisbt/security/advisories/GHSA-qj6w-v29q-4rgx"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-39960"},{"type":"FIX","url":"https://github.com/mantisbt/mantisbt/commit/5fec0f448b7a7d7d539a6adb6dccceac4e4e4ab7"},{"type":"PACKAGE","url":"https://github.com/mantisbt/mantisbt"},{"type":"WEB","url":"https://mantisbt.org/bugs/view.php?id=37003"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-12T03:51:43.953374191Z"}}