'hpPostProcessing.bundle' malware?

User ewayte found the main reason. It's part of the link he supplied:

From sources familiar with the matter that HP Inc asked Apple to revoke its printer driver code-signing certificates. It appears this request backfired as it left users unable to print. A HP Inc spokesperson told us on Friday night:

We unintentionally revoked credentials on some older versions of Mac drivers. This caused a temporary disruption for those customers and we are working with Apple to restore the drivers. In the meantime, we recommend users experiencing this problem to uninstall the HP driver and use the native AirPrint driver to print to their printer.

perhaps the certificates are expired.

i solved the issue:

remove the printer on Settings > Printers & Scanners

trash the folder /library/printers/hp

reinstall the printer with using airprint driver

HP has fixed the drivers with new signature. You have to install this package. Worked for me.

ftp://ftp.hp.com/pub/softlib/software12/HP_Quick_Start/osx/Installations/Essentials/hp-printer-essentials-S-5_14_8_4.pkg

Problem solved (for me). I've downloaded the 5.1 driver from Apple. They have updated the drivers. After installation, I have to delete the printer in System Preferences, add it new and all works fine.

https://support.apple.com/kb/DL1888

Another fix we have recently found is to delete the HP folder located in users library-printers, empty the trash bin and then restart the machine. After restarting the machine in printer & scanners delete the HP printer and reinstall using IP using the HP Jetdirect - Socket protocol. You will then be promoted if you would like to download the driver from apple. Once downloaded, the correct driver will be auto selected and you are able to print. I have done this on 3 Macs now running 10.15.7.

I hope you've solved your problem by now, but you don't need to buy a new printer. I started to think that too but found help in the link below. Just follow this link to upgrade your HP printer software (via Apple) to 5.1. Then delete your printer and reinstall. It will work after that.

Problem solved (for me). I've downloaded the 5.1 driver from Apple. They have updated the drivers. After installation, I have to delete the printer in System Preferences, add it new and all works fine.

https://support.apple.com/kb/DL1888

It is not malware, it is a certificate withdraw that was accidentally perpetrated by apple after a request by hp. Some people seem to manage by just reinstalling the standard driver pack.

apple should be issuing an upgrade imminently but meantime try the link two messages up and failing that, put a generic driver in place.

No need to trash anything.

A fix was provided rather quickly. Do the following:

A. Get the most recent HP drivers, either from:

     ftp://ftp.hp.com/pub/softlib/software12/HP_Quick_Start/osx/Installations/Essentials/hp-printer-essentials-S-5_14_8_4.pkg

          or

     HP Printer Drivers v5.1 for OS X

          or

     System Preferences > Software Update (if you don't see it, press Command+R)

B. Run the installer.

C. When the installer completes, go to System Preferences > Printers & Scanners, highlight the HP printer and remove it. Then add it back. This is necessary because otherwise it will continue to use the now unsigned drivers and it will appear that the problem has not been fixed. Apparently installing the update does not remove the old drivers.

A note on AirPrint: Your Mac may say it can’t find the AirPrint printer. If that should happen, reboot your router.

I deleted the printer in preferences, reinstalled the driver from this page: https://support.hp.com/in-en/document/c05900790, reconnected the printer and now it works. I have a Laserjet P2015dn printer. Hope it works for other people

Some 32-bit applications (including Drivers) are no longer supported in Catalina. HP knows this, and should have re-compiled their drivers to comply.

Contact HP for an updated version and support.

There are links posted above for two sets of Drivers.

• For "dumb" inkjet printers, use the link that starts with ftp:

• For smarter printers and laserjets, use the link for Drivers version 5.1

In either case, you must delete you old print queue and AFTER download re-add a new Print queue, which will then incorporate the new drivers.

You did Not have to go buy a different printer. Almost none of the others who have posted on the now 6 pages of posts here had to do that.

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If you don't see it in Software Update, Apple now has it posted as a separate, manual download.

HP Driver update 5.1

https://support.apple.com/kb/dl1888?locale=en_US

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what you will need to do:

delete your old Printer Queue,

restart your Mac,

download new Drivers,

Add-A printer to get your full original functions back.

You should not have to fall back to generic postscript driver or AirPrint driver, but those remain as work-arounds.

We are also having the same issues. The work around we currently found was to reinstall the printer using "Generic postscript printer" and not the actual driver. So far this seems to work, and is a temporary solution for now.

A new update was pushed out yesterday - with not enough press coverage it would seem

Try this

ftp://ftp.hp.com/pub/softlib/software12/HP_Quick_Start/osx/Installations/Essentials/hp-printer-essentials-S-5_14_8_4.pkg

This has made my day a whole lot better!

The only thing I did was download the software driver from Apple at: https://support.apple.com/kb/DL1888?locale=en_US.

I learned this from another person on this thread. This should be the solution shown to others.

My HP Color LaserJet CP2025 that I purchased 11 yrs ago started working