Source : Free On-Line Dictionary of Computing

bug-compatible
     
        Said of a design or revision that has been badly compromised
        by a requirement to be compatible with {fossil}s or
        {misfeature}s in other programs or (especially) previous
        releases of itself. "{MS-DOS} 2.0 used \ as a path separator
        to be bug-compatible with some cretin's choice of / as an
        option character in 1.0."
     
        [{Jargon File}]