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Servers and applications

CVE-2021-27889

Nested Auto URL persistent XSS

Severity
Medium 6.1
Published
10 Mar 2021
Last changed
17 Jun 2026
Added to UpHeron
1 Nov 2026
Fixed in
1.8.26
Also known as
GHSA-xhj7-3349-mqcm
Sources
NVD, Project advisories (GitHub)

Description

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

Affected software

SoftwareAffected versions
MyBBServers and applications · cpe:a:mybb:mybb
  • Every version before 1.8.26
MyBBServers and applications · github:mybb/mybb
  • Every version before 1.8.26

References

  • NVD https://nvd.nist.gov/vuln/detail/CVE-2021-27889
  • CVE.org https://www.cve.org/CVERecord?id=CVE-2021-27889
  • GitHub Advisory Database https://github.com/advisories/GHSA-xhj7-3349-mqcm
  • github.com https://github.com/mybb/mybb/security/advisories/GHSA-xhj7-3349-mqcm