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CVE-2024-35218: Umbraco CMS Vulnerable to Stored XSS on Content Page Through Markdown Editor Preview Pane

• Severity: medium (CVSS 4.8 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.4% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2024-05-21 · updated 2026-06-17
• Weakness: CWE-79

Description

Umbraco CMS is an ASP.NET CMS used by more than 730.000 websites. Stored Cross-site scripting (XSS) enable attackers that have access to backoffice to bring malicious content into a website or application. This vulnerability has been patched in version(s) 8.18.13, 10.8.4, 12.3.7, 13.1.1 by implementing IHtmlSanitizer.

Affected products

• Umbraco-CMS: from 8.0.0 before 8.18.13; from 10.0.0 before 10.8.4; from 12.0.0 before 12.3.7; from 13.0.0 before 13.1.1 — fixed in 10.8.4, 12.3.7, 13.1.1, 8.18.13

How to fix

Upgrade to a fixed version: Umbraco-CMS 10.8.4, 12.3.7, 13.1.1, 8.18.13. Check the vendor advisory for mitigations.

References

• https://github.com/umbraco/Umbraco-CMS/commit/1b712fe6ec52aa4e71b3acf63e393c8e6ab85385
• https://github.com/umbraco/Umbraco-CMS/commit/a2684069b1e9976444f60b4b37a80be05b87f6b6
• https://github.com/umbraco/Umbraco-CMS/commit/cbf9f9bcd199d7ca0412be3071d275556f10b7ba
• https://github.com/umbraco/Umbraco-CMS/commit/d090176272d07500dac0daee7c598aa8bb321050
• https://github.com/umbraco/Umbraco-CMS/security/advisories/GHSA-gvpc-3pj6-4m9w
• https://github.com/umbraco/Umbraco-CMS/commit/1b712fe6ec52aa4e71b3acf63e393c8e6ab85385
• https://github.com/umbraco/Umbraco-CMS/commit/a2684069b1e9976444f60b4b37a80be05b87f6b6
• https://github.com/umbraco/Umbraco-CMS/commit/cbf9f9bcd199d7ca0412be3071d275556f10b7ba
• https://github.com/umbraco/Umbraco-CMS/commit/d090176272d07500dac0daee7c598aa8bb321050
• https://github.com/umbraco/Umbraco-CMS/security/advisories/GHSA-gvpc-3pj6-4m9w

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