No, Signal has not been hacked. However, we do recommend turning off showing Signal content in notifications because the content is stored in memory on device. Apparently, this memory can be retrieved if an attacker has physical access to an unlocked device and has the right tool.

https://activistchecklist.org/signal/#signal-disable-notifications

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@HasSignalBeenHacked uhm... if an attacker has access to the unlocked device...... why wouldn't he just open signal? (And no, I did actually not read the article, usually I do before asking stuff like that, but news like these have often bugged me in some CVE related disclosures as well.)

@jesterchen @HasSignalBeenHacked this is about the news that agencies were able to access the notification database for the device using digital forensic techniques, i.e. special tools that can access the iOS filesystem -- push notifications turn out to be held unencrypted in a database on the iOS filesystem, and are thus pretty easy for enforcement to get at.

But it doesn't mean that they are able to access the Signal application itself, if the device was off

@caitp @jesterchen @HasSignalBeenHacked
I don't even have this option, Notification Content, in GrapheneOS.
@kete @jesterchen @HasSignalBeenHacked it's a part of the Signal app's settings, I'm not sure if that's what you're referring to, could be iOS-specific