CVE-2015-7225

Tinfoil Devise-two-factor before 2.0.0 does not strictly follow section 5.2 of RFC 6238 and does not "burn" a successfully validated one-time password (aka OTP), which allows remote or physically proximate attackers with a target user’s login credentials to log in as said user by obtaining the OTP through performing a man-in-the-middle attack between the provider and verifier, or shoulder surfing, and replaying the OTP in the current time-step.

Source: CVE-2015-7225