Nextcloud Server is the file server software for Nextcloud, a self-hosted productivity platform, and Nextcloud Office is a document collaboration app for the same platform. Nextcloud Server 24.0.x prior to 24.0.8 and 25.0.x prior to 25.0.1, Nextcloud Enterprise Server 24.0.x prior to 24.0.8 and 25.0.x prior to 25.0.1, and Nextcloud Office (Richdocuments) App 6.x prior to 6.3.1 and 7.x prior to 7.0.1 have previews accessible without a watermark. The download should be hidden and the watermark should get applied. This issue is fixed in Nextcloud Server 25.0.1 and 24.0.8, Nextcloud Enterprise Server 25.0.1 and 24.0.8, and Nextcloud Office (Richdocuments) App 7.0.1 (for 25) and 6.3.1 (for 24). No known workarounds are available.

Nextcloud is an Open Source private cloud software. Versions 24.0.4 and above, prior to 24.0.7, and 25.0.0 and above, prior to 25.0.1, contain Improper Access Control. Secure view for internal shares can be circumvented if reshare permissions are also given. This issue is patched in versions 24.0.7 and 25.0.1. No workaround is available.

Nextcloud server is an open source home cloud implementation. In affected versions users that should not be able to download a file can still download an older version and use that for uncontrolled distribution. This issue has been addressed in versions 24.0.10 and 25.0.4. Users are advised to upgrade. There are no known workarounds for this vulnerability.