I wonder if the signed features of GitHub would have helped here. Probably can't ask all the 3rd party contributors to setup signing commits, but it would help to spot commits not signed.
Someone responsible for release would have to manually keep a list of keys of authorized comiters and check the repository against this list at the very least prior to a release.
Looking at these commits they say mid-2017. Without signatures any previous commit could be by the same author.
Uh, you mean the features of ... Git?