What’s Vulnerable › Vulnerabilities

CVE-2021-41866

• Severity: medium (CVSS 5.4 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.5% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2021-10-26 · updated 2026-06-17
• Weakness: CWE-79

Description

MyBB before 1.8.28 allows stored XSS because the displayed Template Name value in the Admin CP's theme management is not escaped properly.

Affected products

• mybb: before 1.8.28 — fixed in 1.8.28

How to fix

Upgrade to a fixed version: mybb 1.8.28. Check the vendor advisory for mitigations.

References

• https://github.com/mybb/mybb/security/advisories/
• https://github.com/mybb/mybb/security/advisories/GHSA-gxhv-r3m5-6qv7
• https://github.com/mybb/mybb/security/advisories/
• https://github.com/mybb/mybb/security/advisories/GHSA-gxhv-r3m5-6qv7

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