CVE-2026-45115

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.

• CWE-79

• https://github.com/mybb/mybb/releases/tag/mybb_1840
• https://github.com/mybb/mybb/security/advisories/GHSA-p766-qqxv-rfc2
• https://mybb.com/versions/1.8.40

Published

Aug 18, 2026

Last Modified

Sep 8, 2026

Status

Deferred

• How Strix found a critical auth bypass in etcdStrix autonomously discovered a critical authentication bypass in etcd, later designated CVE-2026-33413.
• Autonomous PentestingAI agents that find and validate exploitable vulnerabilities like this one across your applications.
• PR ReviewsPentest every pull request so vulnerable code is caught before it ships to production.
• AI Penetration TestingHow AI-driven penetration testing continuously covers your attack surface.

• CVE-2026-45104MapServer is a system for developing web-based GIS applicati…7.5
• CVE-2026-45106Weblate is a web based localization tool. Prior to version 2…4.6
• CVE-2026-45108Himmelblau is an interoperability suite for Microsoft Azure …8.4
• CVE-2026-45109Next.js is a React framework for building full-stack web app…7.5
• CVE-2026-4511A security vulnerability has been detected in vanna-ai vanna…6.3
• CVE-2026-45112Allocation of Resources Without Limits or Throttling vulnera…7.5
• CVE-2026-45116MyBB is free and open source forum software. Prior to 1.8.40…8.7
• CVE-2026-45117MyBB is free and open source forum software. From 1.8.13 unt…9.8
• CVE-2026-45118MyBB is free and open source forum software. Prior to 1.8.40…9.3
• CVE-2026-45119MyBB is free and open source forum software. Prior to 1.8.40…4.6
• CVE-2026-4512The reCaptcha by WebDesignBy WordPress plugin before 2.0 doe…3.5
• CVE-2026-45120MyBB is free and open source forum software. Prior to 1.8.40…5.4