Google has informed us that on September 13, 2021, a security update will be applied to make Drive file sharing more secure. This update includes changing the URL of non-native Drive content created prior to November 2017 that is shared with anyone with the link. Non-native files are those created outside of Google Workspace, such as Microsoft Office files and PDFs, and uploaded to Drive. Users who have accessed impacted shared files before will have no impact. Users who have not accessed impacted files that are shared with them may need to request access again. 

Between July 26 and August 25, Google will notify impacted users of the pending update and any affected items that they own or manage. 

• For files and folders in My Drive, the owner of the file will be notified. 
• For files and folders in Shared Drives, the manager(s) of the Shared Drive will be notified.

Users are encouraged to update links to affected files and folders where these links are published (i.e. web sites).

YouTube is undergoing a similar security update. Starting July 23, 2021, older Unlisted YouTube videos will be made Private unless you opt out from this change. This is part of a security update to unlisted videos that were uploaded before January 1, 2017. Unlisted content uploaded on or after January 1, 2017 is unaffected by this change. Note that you can continue to change the privacy settings for this content in YouTube Studio at any time, before and after this change takes place. Owners of YouTube unlisted videos should have already received a notice from Google informing them of this change.