CVE-2015-8973: Mybb Merge System

High severity, CVSS 8.3. EPSS: 1.6% chance of exploitation in the next 30 days.

xmlhttp.php in MyBB (aka MyBulletinBoard) before 1.6.18 and 1.8.x before 1.8.6 and MyBB Merge System before 1.8.6 allows remote attackers to bypass intended access restrictions via vectors related to the forum password.

Affected products

• Mybb Merge System: up to and including 1.8.5
• Mybb Mybb: up to and including 1.6.17; version 1.8.0 only; version 1.8.1 only; version 1.8.2 only; version 1.8.3 only; version 1.8.4 only; …

Published 2017-01-31. Last modified 2026-06-17.