If the application wants the item to be removed from the Notification Center, it must ensure that the alert is dismissed by the user or programmatically! However, it is not clear that this also 'expunges' the notifications (and the their contents) from the notification database.i'm guessing not! If this is the case, Signal may have to avoid generating notifications (containing the message body) for disappearing messages. In short, anything that gets displayed as a notification (yes, including 'disappearing' Signal messages) in the macOS Notification Center, is recorded by the OS. While this is true of any app that displays notifications, it's particularly troublesome for Signal users in need of high-level security, like government workers or journalists.Īny malicious third parties would still need to get their hands on your Mac to get into your message history, so as Motherboard pointed out, 'this is not a major threat for most people.' Still, this could be a major security risk for high-level Signal users, since this means that any disappearing messages that popped up in Notification Center can be recovered later, 'even after they are gone within the Signal app.'

Alec Muffett Mac security researcher Patrick Wardle then investigated the issue further, discovering that the 'deleted' Signal messages that remain in the Notification Center are saved on the Mac's disk inside the operating system.

If you are using the desktop app for Mac, check your notifications bar messages get copied there and they seem to persist - even if they are 'disappearing' messages which have been deleted/expunged from the app.

Signal self destructing messages