Nextcloud Tables allows users to to create tables with individual columns. The information which Table (numeric ID) is shared with which groups and users and the respective permissions was not limited to affected users. It is recommended that the Nextcloud Tables app is upgraded to 0.8.1.
https://hackerone.com/reports/2705507
https://github.com/nextcloud/tables/pull/1406
https://github.com/nextcloud/tables/commit/13ca45f1b9f70f694aea81b78bc7416ec840c332
https://github.com/nextcloud/security-advisories/security/advisories/GHSA-rgvc-xr2w-qq45