A bug in Nextcloud Server 17.0.1 causes the workflow rules to depend their behaviour on the file extension when checking file mimetypes.
Exploitability
AV:NAC:LPR:LUI:RScope
S:UImpact
C:HI:HA:H8/CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:HInput Validation