Details of Facebook Inc.'s (FB) most recent hack are becoming clearer. 

"We have been working around the clock to investigate the security issue we discovered and fixed two weeks ago so we can help people understand what information the attackers may have accessed," Facebook said in a blog post. The post added, "Today, we're sharing details about the attack we've found that exploited this vulnerability. We have not ruled out the possibility of smaller-scale attacks, which we're continuing to investigate." 

The tech behemoth revealed Friday the most recent user account hack, to the tune of 50 million users, only materially impacted 30 million accounts. Users' tokens, or keys to the accounts, were accessed, but only 30 million users had their tokens stolen. "Of the 50 million people whose access tokens we believed were affected, about 30 million actually had their tokens stolen," Facebook wrote in a blog post. 

Facebook shares fell in afternoon trading just under 1%.

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The hackers accessed the names and contact info - such as phone numbers and email addresses - of 15 million users. For some users, hackers were able to see information such as username, gender, language, relationship status, religion, hometown, recent locations visited, and place of work. There were 1 million lucky users who were completely unaffected. 

This is the second attack on the platform of this magnitude Facebook has experienced this year, the first one being the Cambridge Analytica scandal. The stock, which got hit hard by both the Cambridge Analytica scandal, and a disappointing earnings and guidance report in July, has fallen 13.71% this year. The tech selloff Wednesday and Thursday, which abated Friday, didn't exactly help Facebook's stock. 

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