When libpsl support is enabled, libcurl fails to enforce the Public Suffix List boundary check when processing a "Set-Cookie" header where the "Domain" attribute explicitly matches an origin host that is itself a public suffix (e.g., "Domain=co.uk" set by "co.uk"). Instead of coercing it into a strict host-only cookie, libcurl saves the cookie with wildcard domain scope (".co.uk"). Consequently, the cookie is inappropriately included in subsequent outbound requests or HTTP redirects to arbitrary sibling subdomains under the same public suffix (e.g., "attacker.co.uk").