The Music Sheet Viewer plugin for WordPress is vulnerable to Arbitrary File Read in all versions up to, and including, 4.1 via the read_score_file() function. This makes it possible for unauthenticated attackers to read the contents of arbitrary files on the server, which can contain sensitive information.
https://plugins.trac.wordpress.org/browser/music-sheet-viewer/trunk/music-sheet-viewer.php#L748