Re:Facebook crawls links in PDFs you send in Messenger
by yawaramin on Saturday October 26, 2019 @01:36PM
(#21365051)
WhatsApp fetches a link preview on the sender's device before the message is encrypted, and packages it up with the message before sending. Depending on how exactly they implement the fetch, they may or may not know what links you sent.
Re:Facebook crawls links in PDFs you send in Messenger
by Sami_Lehtinen on Saturday October 26, 2019 @01:52PM
(#21365144)
At least links in PDF over WA didn't get visited from FB servers. I just personally tested it moments ago.
Re:Facebook crawls links in PDFs you send in Messenger
by Thorrez on Saturday October 26, 2019 @08:57PM
(#21367279)
What's visiting the links? Your phone?
Re:Facebook crawls links in PDFs you send in Messenger
by exadeci on Sunday October 27, 2019 @08:00PM
(#21373304)
Try sending a link immediately and you'll see that it doesn't get a preview.
Give it a few second after pasting it and you'll get the preview, because it gets it from your device.
Re:Facebook crawls links in PDFs you send in Messenger
by imanobody on Saturday October 26, 2019 @04:29PM
(#21365982)
WhatsApp also scans pdf files you send to a contact. Easy to confirm as well: get some random pdf with chinese filename and chinese content. Send it to a contact. Watch the delay in send/receive. Now do the same for any random pdf that's all English. Watch the regular send/receive time occur.
The only conclusion: it takes a little time for a file that's flagged - based on its language - to pass the scanners?
They can then have a single map of phone num -> links rendered between fb and whatsapp.