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.
The product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory.