In mitmproxy 7.0.4 and below, a malicious client or server is able to
perform HTTP request smuggling attacks through mitmproxy. This means
that a malicious client/server could smuggle a request/response through
mitmproxy as part of another request/response's HTTP message body. While
mitmproxy would only see one request, the target server would see
multiple requests. A smuggled request is still captured as part of
another request's body, but it does not appear in the request list and
does not go through the usual mitmproxy event hooks, where users may
have implemented custom access control checks or input sanitization.
Unless you use mitmproxy to protect an HTTP/1 service, no action is required.