Gossip bomb
When someone drops a piece of gossip and then walks away before the ‘bomb’ explodes leaving them with plausible deniability for all the damage. They weren’t ‘gossiping’ they were just ‘sharing information’.
Mandy told her coworkers how Laura made a huge mistake that day and then Mandy left for the day. By the time she came back the next day, the entire office was in an uproar and there was talk about how Laura should be fired. Mandy gossip bombed her coworkers when she should have told her boss about Laura’s mistake.