Update Signal and pay attention when joining groups:
https://www.wired.com/story/russia-signal-qr-code-phishing-attack/
You should continue using Signal. The update is responding to a sophisticated, state-level attack targeting specific groups.
Unless you are a high-value target, you are almost certainly never going to see this in the wild.
If you know you are a high-value target, ask your support.
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