WASHINGTON — Facebook on Wednesday said that the data of up to 87 million users may have been improperly shared with a political consulting firm connected to President Trump during the 2016 election — a figure far higher than the estimate of 50 million that had been widely cited since the leak was reported last month.

Mark Zuckerberg, the company’s chief executive, also announced that Facebook would offer all of its users the same tools and controls required under European privacy rules. The European rules, which go into effect next month, give people more control over how companies use their digital data.

Facebook had not previously disclosed how many accounts had been harvested by Cambridge Analytica, the firm connected to the Trump campaign. It has also been reluctant to disclose how it was used by Russian-backed actors to influence the 2016 presidential election.

Among Facebook’s acknowledgments on Wednesday was the disclosure of a vulnerability in its search and account recovery functions that it said could have exposed “most” of its 2 billion users to having their public profile information harvested.