A logic error in Nextcloud Server 19.0.0 caused a privilege escalation allowing malicious users to reshare with higher permissions than they got assigned themselves.
hackerone.com/reports/889243
lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/KC6HLX5SG4PZO6Y54D2LFJ4ATG76BKOP/
lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/T7FX3O6SJE2S52I2HAA4DSTUIISP5BNA/
nextcloud.com/security/advisory/?id=NC-SA-2020-029