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

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 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.

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

A wrong check in Nextcloud Server 19 and prior allowed to perform a denial of service attack when resetting the password for a user.

A missing link validation in Nextcloud Server before 20.0.2, 19.0.5, 18.0.11 allows execution of a stored XSS attack using Internet Explorer when saving a 'javascript:' URL in markdown format.

A missing input validation in Nextcloud Server before 20.0.2, 19.0.5, 18.0.11 allows users to store unlimited data in workflow rules causing load and potential DDoS on later interactions and usage with those rules.

A missing file type check in Nextcloud Contacts 3.3.0 allows a malicious user to upload malicious SVG files to perform cross-site scripting (XSS) attacks.

A missing file type check in Nextcloud Contacts 3.4.0 allows a malicious user to upload SVG files as PNG files to perform cross-site scripting (XSS) attacks.

Missing validation of server certificates for out-going connections in Nextcloud Social < 0.4.0 allowed a man-in-the-middle attack.

Improper access control in Nextcloud Social app version 0.3.1 allowed to read posts of any user.

Insufficient protection of the server-side encryption keys in Nextcloud Server 19.0.1 allowed an attacker to replace the encryption keys.

A wrong configuration in Nextcloud Server 19.0.1 incorrectly made the user feel the passwordless WebAuthn is also a two factor verification by asking for the PIN of the passwordless WebAuthn but not verifying it.

Missing access control in Nextcloud Deck 1.0.4 caused an insecure direct object reference allowing an attacker to view all attachments.

A memory corruption vulnerability exists in NextCloud Desktop Client v2.6.4 where missing ASLR and DEP protections in for windows allowed to corrupt memory.

A memory leak in the OCUtil.dll library used by Nextcloud Desktop Client 2.6.4 can lead to a DoS against the host system.

A missing rate limit in the Preferred Providers app 1.7.0 allowed an attacker to set the password an uncontrolled amount of times.

Missing sanitization of a server response in Nextcloud Desktop Client 2.6.4 for Linux allowed a malicious Nextcloud Server to store files outside of the dedicated sync directory.

A cleartext storage of sensitive information in Nextcloud Desktop Client 2.6.4 gave away information about used proxies and their authentication credentials.

A code injection in Nextcloud Desktop Client 2.6.4 allowed to load arbitrary code when placing a malicious OpenSSL config into a fixed directory.