Umbraco October 27, 2026 security release: Forms RCE via workflow Razor view (GHSA-6mm6-h9v6-mjmp), back-office account takeover (GHSA-rpv9-qp4c-g469) and 8 more. Which CMS, Forms and Umbraco AI versions fix them?

What it is: Umbraco released fixes for 10 vulnerabilities on October 27, 2026. The two high ones (CVSS 8.8): in Umbraco Forms, a back-office user who can edit form workflow settings can make the server write and render a Razor view, which means code execution on the web server (GHSA-6mm6-h9v6-mjmp); in Umbraco CMS, a manipulated sign-in redirect can lead to back-office account takeover (GHSA-rpv9-qp4c-g469). The rest are moderate or low: stored XSS with path traversal in media, logout not killing the auth cookie, unpublished content leaking through preview and the Delivery API, preview tokens that never expire, start-node permission gaps, Forms entries readable without permission, and an Umbraco AI issue. Am I affected: - Umbraco CMS 17.x up to 17.7.1 or 18.x up to 18.2.1 (13.x up to 13.16.2 only for the start-node permission bug GHSA-r4qv-c8pg-qq59). - Umbraco Forms 13.0.0-13.9.11, 17.0.0-17.6.1 or 18.0.0-18.2.1. - Umbraco AI packages (Umbraco.AI.Core, .Agent, .Agent.Deploy, .Deploy, .Search) on the 17.x/18.x ranges listed in GHSA-xc89-5cg7-36xf. - Umbraco 14, 15 and 16 are end-of-life and get no fixes; treat them as vulnerable. - Check versions with dotnet list package or in the back office (Settings > Info). Fix: 1. CMS: upgrade to 17.7.2 or 18.2.2 (13.16.3 on the 13 LTS line). 2. Forms: upgrade to 13.9.12, 17.6.2 or 18.2.2. 3. Umbraco AI: Core 17.6.1 / 18.6.1, Agent 17.4.1 / 18.4.1, Agent.Deploy 17.1.1 / 18.1.1, Deploy 17.3.1 / 18.3.1, Search 17.0.5 / 18.0.5. If Deploy files with AI provider keys were ever committed to source control, rotate those keys. 4. Umbraco Cloud upgrades CMS and Forms automatically, but Umbraco AI must be upgraded by you. 5. On 14/15/16: plan the move to 17 LTS or 18; a patch-level update is not available. Interim steps from the advisory until you upgrade: set AllowedHosts (or explicit host bindings on the web server or proxy) so the site only answers to its real host names; give Forms section and media create/update rights only to trusted users; disable or don't expose the Delivery API if you don't use it; disabling or locking a user invalidates their preview tokens (a password change does not). Verify: rebuild and redeploy, confirm the new package versions in the deployed bin folder or Settings > Info, and review back-office users and form workflows for unexpected changes. Sources: https://umbraco.com/blog/security-advisory-oct-27-2026-security-patches-for-umbraco-cms-umbraco-forms-and-umbraco-ai-now-available/ https://github.com/umbraco/Umbraco.Forms.Issues/security/advisories/GHSA-6mm6-h9v6-mjmp https://github.com/umbraco/Umbraco-CMS/security/advisories/GHSA-rpv9-qp4c-g469 https://cyber.netsecops.io/articles/umbraco-patches-high-severity-privilege-escalation-vulnerability/