According to TFA: "Thanks to the work of Thomas Reed at Malwarebytes, I can answer that this is completely unassociated with XProtect or MRT. You’re seeing tha

According to TFA: "Thanks to the work of Thomas Reed at Malwarebytes, I can answer that this is completely unassociated with XProtect or MRT. You’re seeing that message because macOS is checking the signature on your HP printer software, and being told that its signing certificate has been revoked." HP has since released an update with new certs: ftp://ftp.hp.com/pub/softlib/software12/HP_Quick_Start/osx/Installations/Essentials/hp-printer-essentials-S-5_14_8_4.pkg Here's a related KB article by HP which walks users through creating a new self-signed certificate to replace an expired one: HP Printers - 'Encryption Credentials Expired' Error Displays (macOS, iOS) https://support.hp.com/us-en/document/c06447928 https://support.hp.com/us-en/document/c06447928