In a first such revelation, Facebook has admitted that data of nearly 5.6 lakh Indian users may have been "improperly" shared with British political analytics company Cambridge Analytica.
In a blog post, Mike Schroepfer, Chief Technology Officer at Facebook, showed country-specific break-up of people affected by the data breach.
While most users are from the US - over 70 million - 562,455 Indian users' data has also been shared with Cambridge Analytica.
"In total, we believe the Facebook information of up to 87 million people - mostly in the US - may have been improperly shared with Cambridge Analytica," Schroepfer wrote.
"Starting on Monday, April 9, we'll show people a link at the top of their News Feed so they can see what apps they use - and the information they have shared with those apps," he added.
People will also be able to remove apps that they no longer want.
"As part of this process, we will also tell people if their information may have been improperly shared with Cambridge Analytica," Schroepfer posted.
In a press conference late on Wednesday, Facebook CEO Mark Zuckerberg said Facebook has a big responsibility when it comes to tackle fake news on its platform this year as several countries are facing general elections.
"This year is going to be an important year for protecting election integrity around the world. There's the Mexican presidential election, there are big elections in India and Brazil, as well as Pakistan and Hungary and a number of other countries, and the US midterms, of course, too," he said.
Facebook now has about 15,000 people working on security and content review, and "we'll have more than 20,000 by the end of this year."
Facebook is also enhancing its security features to ensure the integrity of upcoming key elections in countries like India on its platform.
This comes days after Christopher Wylie, who blew the lid off the Facebook user personal data being illegally used for political purposes, disclosed how his former employer Cambridge Analytica through an Indian arm had conducted election research on behalf of some political parties.
Wylie in a widely shared tweet said SCL Group, the parent organisation of Cambridge Analytica, has its office headquartered in Indirapuram in Ghaziabad and its regional offices in Ahmedabad, Bengaluru, Cuttack, Guwahati, Hyderabad, Indore, Kolkata, Patna and Pune.
"I've been getting a lot of requests from Indian journalists. So here are some of SCL's past projects in India. To the most frequently asked question - yes, SCL/CA works in India and has offices there. This is what modern colonialism looks like," Wylie said.
The SCL India, according to the tweeted document, helped clients to identify and target key groups within the population "to effectively influence their behaviour to realize a desired outcome".
It explained that SCL provided its clients the research to develop and "disseminate the right messages from the right sources using the right communication channels".
It said in 2011, SCL India undertook a state-wide research campaign to identify voter caste by household.
"This booth level polling data formed the basis of further research into swing voter motivation and supporter mobilization strategies which were presented to individual candidates and tailored to their constituencies."
During the 2009 Lok Sabha elections, SCL India managed the campaign of a number of Lok Sabha candidates.
"The research and campaign teams employed SCL India's proprietary data collection methodologies to form strategies that gave the clients successful election campaigns."
Wylie, 28, was the Director of Research at Cambridge Analytica. He accused the data analytics firm having influenced the result of the United Kingdom's 2016 Brexit referendum and of the 2016 American presidential election that brought Donald Trump to the White House.
Speaking to the British MPs, Wylie said Cambridge Analytica worked extensively in India.
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