Plack::Middleware::Session::Cookie versions through 0.21 for Perl allows remote code execution. Plack::Middleware::Session::Cookie versions through 0.21 has a security vulnerability where it allows an attacker to execute arbitrary code on the server during deserialization of the cookie data, when there is no secret used to sign the cookie.
https://metacpan.org/release/MIYAGAWA/Plack-Middleware-Session-0.23-TRIAL/changes