Keys used to sign EU Digital Covid Certificates may have been leaked
twitter.com
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The EU DCC spec is decentralized, so it is very unlikely that more than one country got owned.
Honestly, I don't really mind that because I am not really a fan of vaccination certificates for an extended period of time.
edit: Seems to be fixed, so the key probably wasn't leaked.
Maybe the update is not complete and takes longer time for some countries. Or the app does not check for revocation lists etc. I don't know the technical details.