Python 2.7.x through 2.7.16 and 3.x through 3.7.2 is affected by improper Handling of Unicode Encoding (with an incorrect netloc) during NFKC normalization. A specially crafted URL could be incorrectly parsed by urllib.parse.urlsplit and urllib.parse.urlparse to locate cookies or authentication data and send that information to a different host than when parsed correctly.