GHSA-px8h-6qxv-m22q Incorrect parsing of nameless cookies leads to __Host- cookies bypass

• PyPI Werkzeug: < 2.2.3 → fixed in 2.2.3

Browsers may allow "nameless" cookies that look like `=value` instead of `key=value`. A vulnerable browser may allow a compromised application on an adjacent subdomain to exploit this to set a cookie like `=__Host-test=bad` for another subdomain. Werkzeug <= 2.2.2 will parse the cookie `=__Host-test=bad` as `__Host-test=bad`. If a Werkzeug application is running next to a vulnerable or malicious subdomain which sets such a cookie using a vulnerable browser, the Werkzeug application will see the bad cookie value but the valid cookie key.