[agakshat]

The linked page [1] says that Whatsapp does not share contact list with Facebook. I have a lot of anecdotal evidence which suggests otherwise, where adding new contacts would immediately have them show up in my list of suggested friends on Facebook, even without any mutual friends. My experiences are from >3 years ago, though, after when I stopped using Facebook.

[1] https://faq.whatsapp.com/general/security-and-privacy/answer...

[curiousgal]

I have the same experience but it could be due to those contacts installing Messenger/Facebook and sharing your number with Facebook:

Contact has your number and shares it with Facebook.

Your Facebook account has your number.

The link is made.

[jobigoud]

Ah yes the same link that allowed patients of a psychologist to suddenly know about each other.

[Spivak]

I suspect it's something like Facebook knows both your and their phone number, sees a WhatsApp messages between them, and connects the dots. Technically there wasn't any contact sharing.

[fmajid]

They were fined $122M by the EU for doing precisely that 3 years ago.

https://www.theverge.com/2017/5/18/15657158/facebook-whatsap...