go-f3 is a Golang implementation of Fast Finality for Filecoin (F3). In versions 0.8.8 and below, go-f3’s justification verification caching mechanism has a vulnerability where verification results are cached without properly considering the context of the message. An attacker can bypass justification verification by submitting a valid message with a correct justification and then reusing the same cached justification in contexts where it would normally be invalid. This occurs because the cached verification does not properly validate the relationship between the justification and the specific message context it’s being used with. This issue is fixed in version 0.8.9.