Authenticated XSS in GitLab Markdown Placeholder Processing
CVE-2026-1090 is a high-severity cross-site scripting vulnerability in GitLab CE/EE markdown processing. It affects GitLab CE/EE all versions from 10.6 before 18.7.6, 18.8 before 18.8.6, and 18.9 before 18.9.2. When the markdown_placeholders feature flag is enabled, improper sanitization of placeholder content during markdown placeholder processing can allow an authenticated user to inject attacker-controlled JavaScript into a victim’s browser.
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Impact, mitigation & remediation
What it means. What to do now. Patch path, mitigations, and the assume-compromise checklist.
Impact
What an attacker gets, and what they’ve been doing with it.
Mitigation
If you can’t patch tonight, do this now.
markdown_placeholders feature flag where operationally feasible, since the provided context states exploitation requires that feature flag to be enabled. Standard XSS risk reduction measures such as limiting exposure to untrusted authenticated users may reduce risk, but the primary mitigation in the provided content is to patch or avoid the vulnerable feature configuration.Remediation
Patch, then assume compromise.
Exploits
No public exploits tracked yet. Mallory keeps watching.
No public exploit code observed for this vulnerability.
Affected products & vendors
Products and vendors Mallory has correlated with this vulnerability. Open in Mallory to drill down to specific CPE configurations and version ranges.
Vendor-confirmed product mapping. Mallory continuously reconciles this list against your asset inventory.
Recent activity
10 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.
A high-severity cross-site scripting (XSS) vulnerability in GitLab Markdown placeholder processing (when the feature flag is enabled) that allows an authenticated attacker to bypass sanitization and inject malicious JavaScript into a victim’s browser.
An improper sanitization vulnerability in GitLab CE/EE markdown processing (when the `markdown_placeholders` feature flag is enabled) that could allow an authenticated user to inject JavaScript in a victim's browser (XSS).
The version that knows your environment.
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.