Farzan Hussain writes:
Hackers can use a security exploit in Facebook to “decrypt and sniff out” IDs of Facebook users by using one of the vulnerable Facebook API. Allowing them to gain access to the personal information of millions of Facebook users including their name, location, phone number, pictures and other personal data.
Read more on HackRead – and keep reading so that you read Facebook’s response to the researcher’s multiple attempts to get them to take the vulnerability more seriously.