Python Improper Input Validation Vulnerability - CVE-2018-20852

http.cookiejar.DefaultPolicy.domain_return_ok in Lib/http/cookiejar.py in Python before 3.7.3 does not correctly validate the domain: it can be tricked into sending existing cookies to the wrong server. An attacker may abuse this flaw by using a server with a hostname that has another valid hostname as a suffix (e.g. pythonicexample.com to steal cookies for example.com). When a program uses http.cookiejar.DefaultPolicy and tries to do an HTTP connection to an attacker-controlled server existing cookies can be leaked to the attacker. This affects 2.x through 2.7.16 3.x before 3.4.10 3.5.x before 3.5.7 3.6.x before 3.6.9 and 3.7.x before 3.7.3.