CVE-2026-45115 MyBB: Buddy/ignore list username XSS
Attackers can inject JavaScript via crafted usernames in MyBB buddy/ignore lists, potentially leading to code execution or account takeover.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- None listed
What is CVE-2026-45115?
CVE-2026-45115 is a high-severity cross-site scripting vulnerability in mybb, published on 18 Aug 2026. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.
Official description
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.
Weakness: CWE-79
Which versions are affected by CVE-2026-45115?
How do I fix CVE-2026-45115?
No fix has been published for CVE-2026-45115 yet. Limit exposure of the affected software until one is available.
Escape output for the context it lands in and set a strict Content Security Policy. Upgrading the affected component is the real fix. More about Cross-site scripting.
Is CVE-2026-45115 being exploited?
There is no known exploitation of CVE-2026-45115 in the wild and no public exploit code.
Sources
Also known as GHSA-p766-qqxv-rfc2.