CVE-2025-66554: Nextcloud Contacts

Medium severity, CVSS 5.4. EPSS: 0.3% chance of exploitation in the next 30 days.

Contacts app for Nextcloud easily syncs contacts from various devices with your Nextcloud and allows editing. Prior to 5.5.4, 6.0.6, and 7.2.5, a malicious user was able to modify their organisation and title field to load additional CSS files. Javascript and other options were correctly blocked by the content security policy of the Nextcloud Server code. This vulnerability is fixed in 5.5.4, 6.0.6, and 7.2.5.

Affected products

• Nextcloud Contacts: from 5.0.0, before 5.5.4 (fixed in 5.5.4); from 6.0.0, before 6.0.6 (fixed in 6.0.6); from 7.0.0, before 7.2.5 (fixed in 7.2.5)

Published 2025-12-05. Last modified 2026-06-17.