Nextcloud Server is a self hosted personal cloud system. After an admin enables the default-disabled SVG preview provider, a malicious user could upload a manipulated SVG file referencing paths. If the file would exist the preview of the SVG would preview the other file instead. It is recommended that the Nextcloud Server is upgraded to 27.1.10, 28.0.6 or 29.0.1 and Nextcloud Enterprise Server is upgraded to 24.0.12.15, 25.0.13.10, 26.0.13.4, 27.1.10, 28.0.6 or 29.0.1.
https://hackerone.com/reports/2484499
https://github.com/nextcloud/server/pull/45340
https://github.com/nextcloud/server/commit/7e1c30f82a63fbea8c269e0eec38291377f32604
https://github.com/nextcloud/security-advisories/security/advisories/GHSA-5m5g-hw8c-2236