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  1. 1

    I assumed that the redacted app would be Telegram, but in the comments on the Ars Technica story one of the authors clarified it’s not:

    I am curious how Telegram fairs.

    We tested a lot of apps, but we somehow missed Telegram in our final write-up.

    I can tell you how it behaves:

    In normal chats, Telegram generates link previews server-side. The server downloads up to 20 MB of > any file.

    In secret chats, that are end-to-end encrypted, Telegram prompts the user if they want to enable the feature of link previews. If enabled, the sender will generate the link previews and send it as an attachment to the receiver, i.e. it follows Approach 1 according to our article.