important · Signal for iOS
A registered Signal user can alter pin and poll state in an unrelated group on one victim’s iPhone.
Affects
Signal for iOS, the encrypted messaging client running on iPhone and iPad
Signal authorizes the sender against an attacker-selected contact thread, then uses a global thread-blind index to resolve an interaction in another group. That permits recipient-local pin removal or corruption and an unauthorized poll vote.
Detail and 2 sources
The attacker needs the target message’s timestamp and author ACI, which is most practically learned through former group membership. Signal 8.7.0.1523 is identified as the fixed release.