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> If users access WhatsApp through a web browser, the service can also collect information about websites visited before and after sending messages, Collins added.

Whoa, how would they do that? Or is that just a british MP not knowing what he's talking about?

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Referrer header and rewriting links in messages?

Through third-party cookies such as the Facebook pixel.

There have also always been tricks to get that information for popular sites, like explained in the Browser history revisited [0] paper.

[0]: https://cseweb.ucsd.edu/~dstefan/pubs/smith:2018:browser.pdf

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