CVE-2021-27889: Mybb

Medium severity, CVSS 6.1. EPSS: 5.1% chance of exploitation in the next 30 days.

Cross-site Scripting (XSS) vulnerability in MyBB before 1.8.26 via Nested Auto URL when parsing messages.

Affected products

• Mybb Mybb: before 1.8.26 (fixed in 1.8.26)

Published 2021-03-15. Last modified 2026-06-17.