XSS in Mybb Cross-Poster
CVE-2021-39338
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.
Vulnerability class: XSS (Cross-Site Scripting)
EPSS: 0.009 (58.2th percentile) — read the EPSS interpretation.
CVSS v3 metric
CVSS v3 base score 5.5 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:L/I:L/A:N.
Affected products
- Mybb Cross-poster — versions 1.0
- Mybb_cross-poster_project Mybb_cross-poster
Weakness classification (CWE)
Public proof-of-concept exploits
References
- security@wordfence.com (Third Party Advisory, x_refsource_MISC)
- security@wordfence.com (Exploit, Third Party Advisory, x_refsource_MISC)
- security@wordfence.com (Patch, Third Party Advisory, x_refsource_MISC)
Frequently asked questions
- What is CVE-2021-39338?
- CVE-2021-39338 is a medium-severity vulnerability in Mybb Cross-Poster, classified under Cross-site Scripting. CVSS score: 5.5/10. Published 2021-10-15.
- How severe is CVE-2021-39338?
- Medium severity. CVSS v3 base score is 5.5 out of 10.
- Is CVE-2021-39338 known to be exploited?
- 1 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.