Former Yahoo Chief Executive Marissa Mayer apologised on Wednesday for two massive data breaches at the internet company, blaming Russian agents for at least one of them, at a hearing on the growing number of cyber attacks on major U.S. companies. “As CEO, these thefts occurred during my tenure, and I want to sincerely apologise to each and every one of our users,” she told the Senate Commerce Committee, testifying alongside the interim and former CEOs of Equifax Inc and a senior Verizon Communications Inc executive.