CVE-2021-39338

MEDIUM

MyBB Cross-Poster < 1.0 - Authenticated Stored Cross-Site Scripting via MyBBXPSettings.php Parameters

Title source: llm

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.

References (3)

Core 3

Core References

Third Party Advisory x_refsource_misc

https://www.wordfence.com/vulnerability-advisories/#CVE-2021-39338

Exploit, Third Party Advisory x_refsource_misc

https://github.com/BigTiger2020/word-press/blob/main/MyBB%20Cross-Poster.md

View Exploit ZIP pw:eip

Patch, Third Party Advisory x_refsource_misc

https://plugins.trac.wordpress.org/browser/mybb-cross-poster/trunk/classes/MyBBXPSettings.php

Scores

CVSS v3 5.5

EPSS 0.0092

EPSS Percentile 55.4%

Attack Vector NETWORK

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

CISA SSVC

Vulnrichment

Exploitation none

Automatable no

Technical Impact partial

Details

CWE

CWE-79

Status published

Products (1)

mybb_cross-poster_project/mybb_cross-poster < 1.0

Published Oct 15, 2021

Tracked Since Feb 18, 2026