When a user writes workaround code to deal with a software bug, and then the programmer later fixes the bug which breaks the workaround code. It is not hackward compatible.
User: This update broke the software!
Programmer: No, the update fixes the software, it simply is not hackward compatible.
Programmer: No, the update fixes the software, it simply is not hackward compatible.
by FenderQ September 1, 2019