CVE-2026-34566 is a critical stored cross-site scripting flaw in CI4MS, a CodeIgniter 4 based CMS. NVD scores it 9.1. Several fields in page create and edit forms accept script content that is stored and then rendered without output encoding in admin lists and public pages. Upgrade to ci4ms 0.31.0.0 or later.
What's affected
CI4MS (ci4-cms-erp ci4ms) versions before 0.31.0.0. The fixed release is 0.31.0.0.
Any site running an older build with the affected feature reachable to a signed in user is in scope.
How to check if you're exposed
Find the ci4ms version your site runs. If you deployed from a git checkout, git describe --tags in the project folder shows the nearest release tag. Otherwise look at the release or commit you installed from.
Anything older than 0.31.0.0 is in scope. The record names no workaround, so the version number is the test. The advisory linked under Sources lists the exact affected range.
What to do now
- Upgrade ci4ms to 0.31.0.0 or later and redeploy.
- Until you can, limit who holds accounts that can create or edit pages, and review those accounts.
- Look through existing page records for entries that contain script tags or event handler attributes, and clean them.
- Sign out active sessions for administrators after the upgrade.
Why it matters
The weakness class is CWE-79, cross-site scripting. Multiple input fields in the page create and edit forms accept content that is stored and later rendered in administrative page lists and public page views without encoding.
Stored XSS is worse than the reflected kind because the script waits in the database and runs for every person who later opens the page. The CVSS vector has Scope Changed, which reflects that the script runs in the browser of someone else, often an administrator. The usual fix is output encoding on every place the stored value is rendered, plus input validation.
The record does not flag this CVE as listed in CISA's Known Exploited Vulnerabilities catalog, and the advisory I read does not say it is exploited.
Quick check
Which pages are exposed to visitors?
The record says the stored values appear in public facing page views as well as in admin lists, so ordinary visitors can be affected and not only staff.
Sources
Last reviewed: 19 October 2026.
