"So basically, theres two players here: Cellebrite and Signal.
Cellebrite is israeli software that, when plugged into a phone, can download the entire contents of the phone and then index (make it searchable by keywords) and display it in a nice report.
Imagine cops get a drug dealers phone, and want to show that he has been selling drugs. Well they COULD have an officer scroll through every text that has been sent, screenshot all the times where money changed hands, and then send it to the DA. With Cellebrite though, they just tell it to search for any time money and weight were discussed and then celllebrite sends a report off to the DA all nicely formatted and containing the source files to boot. neat! very convenient.
WELL cellebrite does this using what is considered 'gray' techniques because if anyone else did it, it would be illegal. but because it is for cops, the hacking is allowed. Just like if you run Kali, thats totally legal, right up until you use it for what its meant to be used for since you're not a cop. BTW, you should totally run kali.
So a few months ago, Cellebrite announces "Hey, we can now parse signal data too" Which was a big deal because signal is marketed as 'stay safe from the gubment'
SO signals lead engineer, and CEO, says 'well fuck that' so he buys one of those on the black market, and hacks it. he discovers a few vulnerabilities in it that allow him to install any code he wants on the source device.
So he writes a blog post beating around the bush saying:
"Hey did you guys know that Cellebrite is gonna start hacking signal? well did you also know that cellebrite is vulnerable to the point where arbitrary code can be executed that can edit the reports it sends to the DA? both past and future reports? isnt that something? you know, their bug is so bad that i can make it look like it was never hacked at all, the fingerprint of the file wont change so there would be nothing they could do, all cellebrite data would be inadmissible in court! isnt that crazy?! i would never do that though. Unrelated, im gonna install some files randomly on some of you guys' phones. dont worry about it. they dont do anything as far as your phone is concerned."
He basically spelled it out saying: Someone can make all your evidence moot, and youd have know way of knowing, and id totally never do that because it would be illegal. but i did. and im telling you about it. your move, bitch"