If decryption fails due to a missing integrity check (MDC) then Kleopatra shows a "Force Decryption" button. This allows the user to ignore the missing integrity check and to force decryption with GnuPG.

I think this button should be removed. I think nowadays ignoring a missing integrity check on decryption is an absolute no-go. Therefore we shouldn't make it easy for people to shoot themselves in the foot. People who need to decrypt decades old data without MDC should use the command line. (We could show a hint in Kleopatra in case decryption fails because of missing MDC.)

I stumbled over this while looking into T7784: Kleopatra notepad: change to buttons in result list widget.

Some background information: The button was added with T4038: Kleopatra: Improve handling of MDC errors. It's only shown for legacy algorithms without MDC, i.e. if AES is used then decryption simply fails without more specific errors (see T4402: Kleopatra decrypt error - Missing MDC for non legacy algos).

You can create a file to test a missing MDC with

gpg --encrypt --rfc2440 --cipher-algo 3des -r 11A9C6D06717C4E284960BA906E28F5FB5297489 --output decrypt-me-no-mdc.gpg encrypt-me.txt

This encrypts the file encrypt-me.txt with the Edward Tester 2023 key.