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CVE-2021-39338

MEDIUM 4.8 CVSS 3.1
Published
October 15, 2021
Last modified
June 17, 2026
NVD status
Modified
Reported by
security@wordfence.com
Weakness
CWE-79
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:C/C:L/I:L/A:N

Description

The MyBB Cross-Poster WordPress plugin is vulnerable to Stored Cross-Site Scripting due to insufficient input validation and sanitization via several parameters found in the ~/classes/MyBBXPSettings.php file which allowed attackers with administrative user access to inject arbitrary web scripts, in versions up to and including 1.0. This affects multi-site installations where unfiltered_html is disabled for administrators, and sites where unfiltered_html is disabled.

Affected WordPress components

A confirmed match is backed by the plugin or theme slug. A possible match is based on the product name only and should be verified.

Affected products and versions

  • MyBB Cross-Poster MyBB Cross-Poster — From 1.0 (including) to 1.0 (including)
  • mybb_cross-poster_project mybb_cross-poster — Up to and including 1.0

References

  • github.com https://github.com/BigTiger2020/word-press/blob/main/MyBB%20Cross-Poster.md Exploit, Third Party Advisory
  • plugins.trac.wordpress.org https://plugins.trac.wordpress.org/browser/mybb-cross-poster/trunk/classes/MyBBXPSettings.php Patch, Third Party Advisory
  • www.wordfence.com https://www.wordfence.com/vulnerability-advisories/#CVE-2021-39338 Third Party Advisory
  • nvd.nist.gov Official NVD record