Thanks to Mr Macintosh for spotting this. Update: The previously revoked signature has now been unrevoked, as of the night of 24-25 October. If you’re interested in Mac security, you might like to follow Thomas on Twitter, the meantime, all you can do is make alternative arrangements to support any HP printers affected, I’m afraid. As soon as we know anything more, I’ll update this article. Thomas Reed has raised this revocation with Apple. So different versions of macOS may well behave differently when Apple revokes certificates. As I’ve recently reported, that hasn’t been updated for over a year now, and Catalina doesn’t seem to even open it any more. Until a year ago, we thought that the certificate revocation database was stored locally, in what we termed the Gatekeeper security database. This may well be because they’re working with different databases. So why don’t earlier versions of macOS reflect the same revocation? Maybe this certificate is being abused on other software which is behaving maliciously? If you’re uncertain what’s going on, contact Apple Support, and the vendor of the software, who may be able to provide further information. You can’t argue, and should next wonder why this might have happened.

macOS therefore won’t allow you to run this software. If you’re not adept at doing that in Terminal, open my free ArchiChect, drag and drop the item onto it to see its report.Īt the top of the text you’ll see a line starting with a No Entry sign: this indicates a serious signature error, in this case indicating the code signing certificate has been revoked. If you ever see an error alert reporting this type of problem, first check the signature on the software that it refers to.

What’s strange, though, is that this doesn’t appear to affect High Sierra and older versions of macOS. 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because macOS is checking the signature on your HP printer software, and being told that its signing certificate has been revoked. Thanks to the work of Thomas Reed at Malwarebytes, I can answer that this is completely unassociated with XProtect or MRT. Could it be that the XProtect update was also broken? Given the recent problems with MRT version 1.68, it’s easy to ascribe this to the same update, although this message clearly isn’t coming from MRT. Many users are today reporting that their HP printer software has suddenly stopped working, with worrying messages implying that their software is malicious and “will damage your computer”.

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