CVE-2026-45115MyBB: Buddy/ignore list username XSS
Updated under an hour ago ()
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No exploitation reported and no EPSS estimate yet.
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MyBB is free and open source forum software. Prior to 1.8.40, the Buddy/Ignore component does not sanitize usernames correctly, allowing attackers to perform JavaScript code injection through a specially crafted username. The User CP Buddy/Ignore list and the Select Buddies list in Private Messages pass usernames through htmlspecialchars_uni(), which may leave single quotes unescaped. The payload is triggered when a victim chooses Yes in Please Confirm while removing the username in usercp.php, or selects the username through the onclick handler in the xmlhttp.php Select Buddies popup. The uniquely identifying implementation details include Private Messages Select Buddies list, and unescaped single quotes. This issue is fixed in version 1.8.40.
- CVSS
- 8.7 HIGH (v3.1, CNA)CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:N
- Weakness (CWE)
- CWE-79
- Known exploited
- Not in CISA's KEV catalog
- EPSS (exploitation in the next 30 days)
- Not loaded for this CVE
- Assigned by
- GitHub_M
- NVD analysis
- Deferred
- Record last updated
- Aug 18, 2026
- First seen by InfoSec Signals
- Oct 9, 2026
Affected products
mybb mybb mybb:mybb (from the name) | before 1.8.40 | CNA record |
References
- https://github.com/mybb/mybb/security/advisories/GHSA-p766-qqxv-rfc2x-refsource-confirm
- https://github.com/mybb/mybb/releases/tag/mybb_1840x-refsource-misc
- https://mybb.com/versions/1.8.40x-refsource-misc
The CVE record on cve.org NVD's entry
The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.