> Wyden’s letter cited a “tip” as the source of the information about the surveillance. His staff did not elaborate on the tip, but a source familiar with the matter confirmed that both foreign and U.S. government agencies have been asking Apple and Google for metadata related to push notifications to, for example, help tie anonymous users of messaging apps to specific Apple or Google accounts.
https://www.schneier.com/blog/archives/2023/12/spying-throug...
> Wyden’s letter cited a “tip” as the source of the information about the surveillance. His staff did not elaborate on the tip, but a source familiar with the matter confirmed that both foreign and U.S. government agencies have been asking Apple and Google for metadata related to push notifications to, for example, help tie anonymous users of messaging apps to specific Apple or Google accounts.