CVE-2026-77912

A stored cross-site scripting (XSS) vulnerability was identified in GitHub Enterprise Server that allowed an authenticated attacker to inject arbitrary HTML attributes into rendered Markdown because the Markdown rendering pipeline rewrote quote characters in already-sanitized HTML without re-sanitizing the result. Crafted Markdown could abuse same-origin JavaScript gadgets to bypass Content Security Policy and gain control of the page DOM when viewed by another user. Successful exploitation could allow an attacker to read content visible to the victim, extract embedded CSRF tokens, perform state-changing actions as the victim, and exfiltrate data through same-origin writes. The payload could also propagate to repositories and organizations where the victim had write access. This vulnerability affected supported GitHub Enterprise Server releases in the 3.17, 3.18, 3.19, 3.20, 3.21, and 3.22 series and was fixed in versions 3.22.1, 3.21.6, 3.20.8, 3.19.12, 3.18.15, and 3.17.21. This vulnerability was reported via the GitHub Bug Bounty program.

• CWE-79

• https://docs.github.com/en/enterprise-server@3.17/admin/release-notes#3.17.21
• https://docs.github.com/en/enterprise-server@3.18/admin/release-notes#3.18.15
• https://docs.github.com/en/enterprise-server@3.19/admin/release-notes#3.19.12
• https://docs.github.com/en/enterprise-server@3.20/admin/release-notes#3.20.8
• https://docs.github.com/en/enterprise-server@3.21/admin/release-notes#3.21.6
• https://docs.github.com/en/enterprise-server@3.22/admin/release-notes#3.22.1

Published

Sep 22, 2026

Last Modified

Sep 24, 2026

Status

Awaiting Analysis

• How Strix found a critical auth bypass in etcdStrix autonomously discovered a critical authentication bypass in etcd, later designated CVE-2026-33413.
• Autonomous PentestingAI agents that find and validate exploitable vulnerabilities like this one across your applications.
• PR ReviewsPentest every pull request so vulnerable code is caught before it ships to production.
• AI Penetration TestingHow AI-driven penetration testing continuously covers your attack surface.

• CVE-2026-77906Heap-based buffer overflow in Visual Studio allows an unauth…8.8
• CVE-2026-77907Heap-based buffer overflow in Visual Studio allows an unauth…8.8
• CVE-2026-77908Improper control of generation of code ('code injection') in…8.8
• CVE-2026-77909Insufficiently protected credentials in Azure CycleCloud all…7.7
• CVE-2026-7791Improper privilege management in the log rotation mechanism …8.5
• CVE-2026-77911Out-of-bounds read in Microsoft Office Word allows an unauth…6.5
• CVE-2026-77914rConfig Core 8.0.0 before 8.2.13 contains a path traversal v…6.5
• CVE-2026-77915rConfig Core 8.0.0 before 8.2.10 contains an authentication …9.8
• CVE-2026-7792The WPForms – Easy Form Builder for WordPress – Contact Form…5.3
• CVE-2026-77923Dolibarr 21.0.0 before 24.0.0 contains an authorization bypa…4.3
• CVE-2026-77927ClipBucket v5 before 5.5.3-#182 contains a blind SQL injecti…6.5
• CVE-2026-77928ClipBucket v5 before 5.5.3-#182 contains a blind SQL injecti…6.5