Cookie integrity bypass via nameless-cookie misparsing

Improper cookie parsing in Pallets Werkzeug before 2.2.3 allows context-dependent attackers to shadow protected cookie values. The _cookie_parse_impl parser searches past a leading equals sign, treats the following protected name as the key, and returns the attacker-controlled value. Exploitation requires a vulnerable browser, a malicious or compromised adjacent subdomain, and a Werkzeug application sharing the parent domain; the bounded result is cookie-value integrity loss.