Nextcloud Server previews are accessible without a watermark

Vulnerability Description

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.

References

• https://github.com/nextcloud/security-advisories/security/advisories/GHSA-92g2-h5jv-jjmg
• https://github.com/nextcloud/richdocuments/pull/2579
• https://github.com/nextcloud/server/pull/34799
• https://hackerone.com/reports/1745755