Facebook has said the attackers gained the ability to "seize control" of those user accounts by stealing digital keys the company uses to keep users logged in.
Hackers captured data from 30 million Facebook users in September.
The vulnerability has now been fixed, but not before the attackers used an automated technique to move from account to account so they could steal the access tokens of users, their friends, friends of their friends, and so on, totalling about 400,000 people. "Of the 50 million people whose access tokens we believed were affected, about 30 million actually had their tokens stolen" said Guy Rosen, the company's vice president of product management, in a statement.
A lucky 1 million users had no information scraped from their accounts by hackers.
Last month, Facebook was hit by the worst-security breach where the hackers accessed personal information of millions of users.
The hackers, who are still unknown, accessed names, email addresses and phone numbers of 15 million Facebook users, said Rosen.
In the coming days Facebook will be sending out personalized messages to each of the accounts compromised, detailing the extent of the information stolen and advice on how to avoid any damage the data theft could cause.
Diablo 3 Nintendo Switch Bundle Announced The bundle is exclusive to GameStop in North America but will also be available in stores in Europe. The back of the Switch console and its dock are also adorned with Diablo designs.
Cyberattackers accessed that data plus additional information including gender, religion, hometown, birth date, and places they had recently "checked in" to as visiting, according to Facebook.
Lawmakers and investors have grown more concerned that Facebook is not doing enough to safeguard data.
The "view as" feature allows users to check their privacy settings by giving them a glimpse of what their profile looks like to others. That included posts on their Facebook timelines, and names of recent Facebook Messenger conversations. Rosen said he can't rule out that the different campaigns exploited the same vulnerability during that time. In late September, Facebook detected unusual activity, discovered the bugs and disabled them.
The breach was the latest privacy embarrassment for Facebook, which earlier this year acknowledged that tens of millions of users had their personal data hijacked by Cambridge Analytica, a political firm working for Donald Trump in 2016.
Facebook said it took a precautionary step of resetting "access tokens" for another 40 million accounts which had accessed the "view as" function. The tech company has now issued an update that allows users to check whether they have been the victim of the data breach.
Rosen declined to say how the attackers went undetected for nearly two weeks as they accessed 30 million accounts.
Third party apps and other Facebook-owned apps like Whatsapp and Instagram were unaffected, the company said.
Despite Bolt's anger, it appears the Australian Sports Anti-Doping Authority guidelines mean he is eligible to be tested. For the latest news, download our app at http://bit.ly/GetALoopJM for Android; and at http://bit.ly/GetiLoopJM for IoS.
After a mediocre start, things clicked in July, when he won at Spa in Belgium, to claim his first victory in the 15th of 30 races. He hugged his team after finishing on the podium for the 13th time in 29 races this season.
One name that has cropped up rather predictably is Arsenal's soon-to-be-out-of-contract midfielder Aaron Ramsey. Man United are one of a number of Premier League rivals of Arsenal's that have already been linked with Ramsey.
Add Donald Trump as an interest to stay up to date on the latest Donald Trump news, video, and analysis from ABC News. Trump and his former personal lawyer, Michael Cohen , want the court to toss out the litigation as moot.
Cuomo has asked the New York State Police and the FBI to assist the NYPD in its investigation of the incident. These three protesters were arrested and freed without bail on charges of burglary and assault.
A security personnel stands at the entrance of Saudi Arabia's consulate in Istanbul, Saturday, Oct. 13, 2018. Trump said Monday the Saudis told him they're working closely with Turkey to find an answer.
The pitch being called for a third strike instead of a walk ended the inning instead of loading the bases in a 2-2 game. Altuve then ripped a single off of the Monster to bring the tying run to the plate in the form of Alex Bregman .
Cole struggles in 2nd playoff start with Astros
Coming into Game 2, the Astros in the 2018 postseason had outscored their opponents 18-1 (!) from the seventh inning onward. The Astros put up deuces in the second and third, the latter highlighted by a two-run Marwin Gonzalez homer.
Kangaroos' new era marred by shock NZ loss
The Kiwis are next in action when they travel to the United Kingdom for a three-Test series against England later this month. Earlier, the Australians started like a freight train with Mitchell putting Valentine Holmes over in just the third minute.
Brewers Hold Off Dodgers To Take Game 1
High-powered Los Angeles had just two singles off starter Wade Miley before breaking through against Milwaukee's vaunted bullpen. George Webb Restaurants has a long-standing promotion to give away a free burger whenever the Brewers win 12 straight.
US, Saudi Arabia on economic collision course
We have seen Saudi Arabia killing Naser al-Sa'id in 1979 in Lebanon - he was kidnapped, taken back to Saudi Arabia and was killed. Saudi journalist Jamal Khashoggi is still missing, almost two weeks after he entered the Saudi Arabian Consulate in Istanbul.
Rescue Efforts Continue in US Amid Hurricane Michael Devastation
Senate against incumbent Democrat Bill Nelson in the November 6 congressional elections in which control of Congress is at stake. Over the weekend, he made a disaster declaration for Georgia's Baker, Decatur, Dougherty, Early, Miller, and Seminole counties.
Google Pixel 3, 3 XL will gain external microphone support
You can access the feature by using the voice command "hey Google, help me interpret..." followed by your language of choice. For those unaware, Google launched its USB-C Pixel earbuds alongside the Pixel 3 and the Pixel 3XL smartphones.