While technically different, both of these vulnerabilities permit that legitimate APKs can be manipulated to replace the original code with arbitrary one without breaking the signature. This allows someone to take an update from a well known publisher (e.g. Google Maps), change the APK, and a device receiving it will happily apply the update as if it was indeed from that publisher. Depending on the apps being updated in this way, priviledge escalation can be achieved.
Google has already mentioned that all apps published on the Play Store are checked for this kind of manipulation, but those of us installing APKs from other sources aren't safe.