NLTK Downloader before 3.4.5 is vulnerable to a directory traversal, allowing attackers to write arbitrary files via a ../ (dot dot slash) in an NLTK package (ZIP archive) that is mishandled during extraction.
https://github.com/nltk/nltk/commit/f59d7ed8df2e0e957f7f247fe218032abdbe9a10
https://github.com/nltk/nltk/blob/3.4.5/ChangeLog
http://lists.opensuse.org/opensuse-security-announce/2020-04/msg00001.html
http://lists.opensuse.org/opensuse-security-announce/2020-03/msg00054.html