Language: Python
Label: safe
CWE: CWE-22 \u2014 Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')
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.

Code:
def __is_within_directory(directory, target):
    abs_directory = os.path.abspath(directory)
    abs_target = os.path.abspath(target)
    prefix = os.path.commonprefix([abs_directory, abs_target])
    return prefix == abs_directory