Facebook shares plunged Thursday by as much as 20% in premarket trading as the social media giant, which is hiking spending to address concerns about data privacy and "fake news" on the platform, warned of slowing growth.

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Chief Executive Mark Zuckerberg said on Wednesday the company “will continue to invest heavily in security and privacy,” adding that the associated cost would likely hurt profitability in upcoming quarters. Facebook has taken steps to address concerns about data privacy and “fake news” on the platform.

Expenses will rise by 50% to 60% this year as Facebook invests in data security, new technology and other initiatives, CFO David Wehner said.

The company missed expectations for second-quarter revenue and reported sagging user growth in key markets after the Cambridge Analytica data breach.

Facebook’s tally of second-quarter global daily active users, a key metric for tracking user engagement, rose 11% to 1.47 billion. Analysts had expected 1.49 billion daily active users. The company reported a total of 2.23 billion monthly active users, below a projected 2.25 billion.

User growth stalled in the key U.S. and Canada region, as the platform’s base 241 million monthly active users was unchanged compared to the first quarter. Monthly users declined slightly in Europe after the implementation of new data privacy regulations in the region.

Revenue also fell short of Wall Street’s expectations, rising 42% to $13.23 billion, less than the $13.36 billion estimate polled by Thomson Reuters. Advertising revenue also fell slightly short of estimates despite rising 42% to $13.04 billion, with mobile advertising accounting for 91% of that total.

T​​​​​he company beat on earnings, which rose 32% to $1.74 per share against an expected $1.72. The social media giant has faced unprecedented scrutiny since reports surfaced that British data firm Cambridge Analytica had improperly accessed the personal data of up to 87 million users.

The second-quarter marked the first full financial period since the data breach became public knowledge.

The after-hours drop in the shares on Wednesday came as the stock hovered at an all-time high with gains of over 21% this year.

This is a breaking story and will be updated.