The document application in ownCloud Server before 6.0.3 uses sequential values for the file_id, which allows remote authenticated users to enumerate shared files via unspecified vectors.
Nextcloud Server before 9.0.52 & ownCloud Server before 9.0.4 are not properly verifying restore privileges when restoring a file. The restore capability of Nextcloud/ownCloud was not verifying whether a user has only read-only access to a share. Thus a user with read-only access was able to restore old versions.
ownCloud Server before 10.3.0 allows an attacker, who has received non-administrative access to a group share, to remove everyone else's access to that share.
Nextcloud Server before 9.0.52 & ownCloud Server before 9.0.4 are not properly verifying edit check permissions on WebDAV copy actions. The WebDAV endpoint was not properly checking the permission on a WebDAV COPY action. This allowed an authenticated attacker with access to a read-only share to put new files in there. It was not possible to modify existing files.