Battle Beacon Virus Abuse
Niantic needs to develop a fix so agents can't use a combination of battle beacons and viruses to upgrade portals to level 8.
They flip to their color. Deploy resonator. Battle Beacon flips it back. Rinse and repeat until level 8. This is an additional unfair advantage for agents with couch portals.
It's still possible without viruses but would require purchasing $30 worth of Battle Beacons instead of one.
A simple fix would be to remove the ability to virus a Battle Beacon portal for up to an hour after the battle completes.