Dancer::Plugin::Auth::Google versions through 0.07 for Perl have TLS verification disabled.
The default user agent is initialised with SSL_verify_mode explicitly disabled.
An attacker with network man-in-the-middle (MITM) capability between the Dancer application and googleapis.com can intercept the OAuth2 token exchange and userinfo fetch, return a forged access_token and user profile, and be logged in to the Dancer application as any Google user.
Weakness
The product does not validate, or incorrectly validates, a certificate.