Nextcloud Server before 9.0.54 and 10.0.1 & ownCloud Server before 9.0.6 and 9.1.2 suffer from content spoofing 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.
https://github.com/owncloud/core/commit/e7acbce27fa0ef1c6fe216ca67c72d86484919a4
https://github.com/owncloud/core/commit/768221fcf3c526c65d85f62b0efa2da5ea00bf2d
https://github.com/nextcloud/server/commit/ed0f0db5fa0aff04594cb0f973ae4c22b17a175a
https://github.com/nextcloud/server/commit/df50e967dbd27b13875625b7dd3189294619b071
https://github.com/nextcloud/server/commit/c3ae21fef2880c9fe44e8fdbe1262ac7f9716f14
https://github.com/nextcloud/server/commit/778ae8abd54c378fc4781394bbedc7a2ee3095e1
https://github.com/nextcloud/server/commit/5dd211cc8845fd4533966bf8d7a7f2a6359ea013
https://github.com/nextcloud/server/commit/1352365e8bf5ea49da3dc82b1ccf7ddb659ae960