CVE-2026-110101

11th percentile - higher than 11% of all known CVEs

Koillection through 1.8.4 contains a stored cross-site scripting vulnerability that allows authenticated users to upload HTML files as Datum file attachments lacking MIME restrictions. Attackers can upload HTML payloads via POST /api/data/{id}/file, served as text/html from public/uploads, executing JavaScript in victims' sessions to perform actions on their behalf.

An attacker can execute arbitrary JavaScript in a victim's browser, hijacking their session and performing actions on their behalf. This poses a serious risk to data confidentiality and integrity within the application.

Update Koillection to a version later than 1.8.4 if available, or enforce MIME restrictions on uploaded files and set Content-Disposition: attachment for files served from the uploads directory.