The vulnerability stems from insecure use of tempfile.mktemp() across multiple test files, which creates predictable temporary filenames without atomically creating the file. This allows local attackers to perform symlink attacks by pre-creating the file or directory. The GitHub commit explicitly replaces mktemp() with secure alternatives (e.g., NamedTemporaryFile, mkdtemp) in these functions, confirming their vulnerability. Each listed function directly used mktemp() in a context where temporary file creation was required, making them clear vectors for the symlink attack described in CVE-2014-1859.