Nextcloud Server is a Nextcloud package that handles data storage. In versions prior to 19.0.11, 20.0.10, and 21.0.2, an attacker is able to receive write/read privileges on any Federated File Share. Since public links can be added as federated file share, this can also be exploited on any public link. Users can upgrade to patched versions (19.0.11, 20.0.10 or 21.0.2) or, as a workaround, disable federated file sharing.

Nextcloud Server is a Nextcloud package that handles data storage. In versions prior to 19.0.11, 20.0.10, and 21.0.2, an attacker is able to convert a Files Drop link to a federated share. This causes an issue on the UI side of the sharing user. When the sharing user opens the sharing panel and tries to remove the "Create" privileges of this unexpected share, Nextcloud server would silently grant the share read privileges. The vulnerability is patched in versions 19.0.11, 20.0.10 and 21.0.2. No workarounds are known to exist.

Nextcloud Server is a Nextcloud package that handles data storage. Nextcloud Server versions prior to 19.0.11, 20.0.10, or 21.0.2 send user IDs to the lookup server even if the user has no fields set to published. The vulnerability is patched in versions 19.0.11, 20.0.10, and 21.0.2; no workarounds outside the updates are known to exist.

Nextcloud Mail is a mail app for the Nextcloud platform. A missing permission check in Nextcloud Mail before 1.4.3 and 1.8.2 allows another authenticated users to access mail metadata of other users. Versions 1.4.3 and 1.8.2 contain patches for this vulnerability; no workarounds other than the patches are known to exist.

Nextcloud Desktop Client prior to 3.1.3 is vulnerable to resource injection by way of missing validation of URLs, allowing a malicious server to execute remote commands. User interaction is needed for exploitation.

The Nextcloud dialogs library (npm package @nextcloud/dialogs) before 3.1.2 insufficiently escaped text input passed to a toast. If your application displays toasts with user-supplied input, this could lead to a XSS vulnerability. The vulnerability has been patched in version 3.1.2 If you need to display HTML in the toast, explicitly pass the `options.isHTML` config flag.

A missing user check in Nextcloud prior to 20.0.6 inadvertently populates a user's own credentials for other users external storage configuration when not already configured yet.

Nextcloud Server prior to 20.0.0 stores passwords in a recoverable format even when external storage is not configured.

Nextcloud Server prior to 20.0.6 is vulnerable to reflected cross-site scripting (XSS) due to lack of sanitization in `OC.Notification.show`.

Nextcloud Deck before 1.0.2 suffers from an insecure direct object reference (IDOR) vulnerability that permits users with a duplicate user identifier to access deck data of a previous deleted user.