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.
Insufficient protection of the server-side encryption keys in Nextcloud Server 19.0.1 allowed an attacker to replace the public key to decrypt them later on.
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.
A logic error in Nextcloud Server 19.0.0 caused a privilege escalation allowing malicious users to reshare with higher permissions than they got assigned themselves.