CVE-2026-45118

MyBB is free and open source forum software. Prior to 1.8.40, the Contact module does not validate a redirect URL or protocol correctly, resulting in an open redirect and reflected JavaScript code injection. contact.php accepts the redirect target from the from HTTP parameter in $mybb->input['from'] or the Referer HTTP header in $_SERVER['HTTP_REFERER'] and passes it to redirect() without sufficient verification. A javascript: URI becomes the target of the `Click here if you don't want to wait any longer` link because $force_redirect is true, allowing script execution when a victim selects the link. This issue is fixed in version 1.8.40.

Referanslar

• https://github.com/mybb/mybb/releases/tag/mybb_1840
• https://github.com/mybb/mybb/security/advisories/GHSA-wf92-5q5h-qr53
• https://mybb.com/versions/1.8.40