Nextcloud Server before 10.0.1 & ownCloud Server before 9.0.6 and 9.1.2 suffer from Stored XSS in CardDAV image export. The CardDAV image export functionality as implemented in Nextcloud/ownCloud allows the download of images stored within a vCard. Due to not performing any kind of verification on the image content this is prone to a stored Cross-Site Scripting attack.

Nextcloud Server before 9.0.54 and 10.0.1 & ownCloud Server before 9.1.2, 9.0.6, and 8.2.9 suffer from SMB User Authentication Bypass. Nextcloud/ownCloud include an optional and not by default enabled SMB authentication component that allows authenticating users against an SMB server. This backend is implemented in a way that tries to connect to a SMB server and if that succeeded consider the user logged-in. The backend did not properly take into account SMB servers that have any kind of anonymous auth configured. This is the default on SMB servers nowadays and allows an unauthenticated attacker to gain access to an account without valid credentials. Note: The SMB backend is disabled by default and requires manual configuration in the Nextcloud/ownCloud config file. If you have not configured the SMB backend then you're not affected by this vulnerability.

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.

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.

Nextcloud Server before 9.0.52 & ownCloud Server before 9.0.4 are vulnerable to a content-spoofing attack in the files app. The location bar in the files app was not verifying the passed parameters. An attacker could craft an invalid link to a fake directory structure and use this to display an attacker-controlled error message to the user.

Nextcloud Server before 9.0.52 & ownCloud Server before 9.0.4 are vulnerable to a log pollution vulnerability potentially leading to a local XSS. The download log functionality in the admin screen is delivering the log in JSON format to the end-user. The file was delivered with an attachment disposition forcing the browser to download the document. However, Firefox running on Microsoft Windows would offer the user to open the data in the browser as an HTML document. Thus any injected data in the log would be executed.

ownCloud Server before 8.1.11, 8.2.x before 8.2.9, 9.0.x before 9.0.7, and 9.1.x before 9.1.3 allows remote authenticated users to cause a denial of service (server hang and logfile flooding) via a one bit BMP file.

The autocomplete feature in the E-Mail share dialog in ownCloud Server before 8.1.11, 8.2.x before 8.2.9, 9.0.x before 9.0.7, and 9.1.x before 9.1.3 allows remote authenticated users to obtain sensitive information via unspecified vectors.

The password reset functionality in ownCloud Server before 8.1.11, 8.2.x before 8.2.9, 9.0.x before 9.0.7, and 9.1.x before 9.1.3 sends different error messages depending on whether the username is valid, which allows remote attackers to enumerate user names via a large number of password reset attempts.

ownCloud server before 8.2.6 and 9.x before 9.0.3, when the gallery app is enabled, allows remote attackers to download arbitrary images via a direct request.

Cross-site scripting (XSS) vulnerability in share.js in the gallery application in ownCloud Server before 9.0.4 and Nextcloud Server before 9.0.52 allows remote authenticated users to inject arbitrary web script or HTML via a crafted directory name.