When I added T75781#787853, the following appeared on T73167 (a task with the "Security" field set to "Security or Sensitive Bug"):
PleaseStand mentioned this in T75781: Cannot view Bugzilla migrated private/security tasks I am author/reporter of.Via Web · Wed, Nov 26, 12:19 PM
Restricted Application changed the visibility of this Task from "Custom Policy" to "Custom Policy". · View Herald TranscriptVia Herald · Wed, Nov 26, 12:19 PM
Restricted Application changed the edit policy of this Task from "Custom Policy" to "Custom Policy". · View Herald Transcript
The old and new custom policies are exactly the same. Same issue as T479?