GHSA-wv64-j4fq-5f9x

When processing a `Set-Cookie` from a response, the `CookieJar` client middleware trusts the server-supplied `Domain` attribute verbatim, with no check that it domain-matches the host that sent the cookie (RFC6265 §5.3 step 6) and no public suffix check. A malicious or compromised server can therefore plant a cookie for any domain in the cookie jar, which is subsequently set on the client's next request to that victim domain, enabling session fixation or overwriting security-relevant cookies.

## Impact

Session fixation and overwrite of security-relevant cookies for arbitrary domains contacted by the same wrapped client.

## Preconditions

- Application uses the `CookieJar` client middleware. - Application contacts an attacker-controlled (or compromised) server using the same jar it uses for trusted hosts.

## Workarounds

- Do not share a `CookieJar` across trusted and untrusted targets.

## Note

This middleware still does not implement public suffix rejection.