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CVE-2026-77912 is a stored cross-site scripting vulnerability in GitHub Enterprise Server's Markdown rendering pipeline. The pipeline rewrites quote characters in HTML that has already been sanitized, but does not sanitize the transformed output. An authenticated attacker can therefore craft stored Markdown that injects arbitrary HTML attributes into rendered content. When another user views the affected Markdown, same-origin JavaScript gadgets can be abused to bypass Content Security Policy and control the page DOM.
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What an attacker gets, and what they’ve been doing with it.
Patch, then assume compromise.
No public exploits tracked yet. Mallory keeps watching.
No public exploit code observed for this vulnerability.
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Vendor-confirmed product mapping. Mallory continuously reconciles this list against your asset inventory.
3 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.
A stored XSS vulnerability in GitHub Enterprise Server's Markdown rendering pipeline. An authenticated attacker could craft Markdown that injects arbitrary HTML attributes, bypasses CSP through same-origin JavaScript gadgets, and executes in a viewing victim's page context, enabling data access, CSRF-token extraction, state-changing actions, exfiltration, and potential propagation to repositories and organizations writable by the victim.
A high-severity stored cross-site scripting flaw in GitHub Enterprise Server's Markdown rendering pipeline. An authenticated attacker could post crafted Markdown that injects arbitrary HTML attributes and executes scripts in a victim's browser, enabling data access, actions as the victim, data exfiltration, and payload propagation using the victim's write permissions.
Query your assets running an affected version, and investigate the blast radius.
Every observed campaign linking this CVE to a named adversary.
Malware families riding this exploit, with evidence and IOCs.
YARA, Sigma, Snort, and vendor rules, auto-deployed to your SIEM.
Cross-references every affected SKU, including bundled OEM variants.
Community discussion across Reddit, Mastodon, and other social sources.