CVE-2021-39338 - CVE House
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Status published Medium CVE-2021-39338

MyBB Cross-Poster <= 1.0 Authenticated Stored Cross-Site Scripting

Vulnerability 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.

Impact Analysis

Refer to official advisory for detailed impact metrics.

Remediation

Ensure systems are updated to the latest vendor-supplied patch levels.

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Credits & Attribution

The following person or organization is credited with identifying this vulnerability, as recorded in the NVD database:

  • Thinkland Security Team

Affected Vendor

MyBB Cross-Poster

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Affected Software

MyBB Cross-Poster
Vulnerable Versions:
1.0

Timeline

Official Publish: October 15th, 2021
Last Modified: March 31st, 2025
Added to House: July 21st, 2026

CVSS Vectors

V3: CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:L/I:L/A:N

Weaknesses (CWE)