Unreported data breaches have disrupted several major M&A deals in recent years, including Marriott International’s merger with the Starwood hotel chain, TripAdvisor Inc.’s acquisition of Viator Inc., and the Verizon-Yahoo Inc. deal. 

When the breaches came to light, they proved costly. Yahoo was devalued by more than $350 million and Verizon became embroiled in a massive class action suit. TripAdvisor shed $580 million in market capitalization. Marriott’s stock took a big hit after the breach was disclosed and the company is still dealing with the fallout, which is believed to have exposed millions of unencrypted and encrypted passport numbers of hotel guests.