CVE-2026-10585: Stored cross-site scripting vulnerability in GitHub Enterprise Server allowed arbitrary JavaScript execution via crafted Discussion titles in the Q&A category

Severity: medium (CVSS 5.4 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.3% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-06-30 · updated 2026-10-25
Weakness: CWE-79

Description

A stored cross-site scripting vulnerability was identified in GitHub Enterprise Server that allowed an authenticated attacker to execute arbitrary JavaScript in another user's browser by injecting a crafted payload into the title of a Discussion in the Q&A category. The AnsweredQuestionStructuredDataComponent did not escape user-controlled Discussion titles before embedding them in a <script type="application/ld+json"> block, allowing the title to break out of the script context. The injection was escalated to a full cross-site scripting attack on GitHub Enterprise Server by leveraging JSONP callback support in the REST API to bypass the Content Security Policy. This vulnerability affected all versions of GitHub Enterprise Server prior to 3.21 and was fixed in versions 3.20.4, 3.19.8, 3.18.11, 3.17.17, 3.16.20. This vulnerability was reported via the GitHub Bug Bounty program.

Affected products

GitHub Enterprise Server: before 3.16.20; from 3.17.0 before 3.17.17; from 3.18.0 before 3.18.11; from 3.19.0 before 3.19.8; from 3.20.0 before 3.20.4 — fixed in 3.16.20, 3.17.17, 3.18.11, 3.19.8, 3.20.4

How to fix

Upgrade to a fixed version: GitHub Enterprise Server 3.16.20, 3.17.17, 3.18.11, 3.19.8. Check the vendor advisory for mitigations.

References

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