There will be many LendingTermOnboarding.sol contracts for every CREDIT token used, but there is no check whether the implementation passed to allowImplementation function is from the same market. 
There can be case when certain gWETH implementation is not allowed in the LendingTermOnboarding for gWETH, but mistakenly allowed in the LendingTermOnboarding for gUSDC. The result will be fully functioning LendingTerm onboarded from wrong contract and potentially malicious behaviour. 
LendingTermOnboarding.sol#L92-L102
Consider checking if the implementation passed is with the same CREDIT token as one in the used in this particular LendingTermOnboarding.
