US-based cloud storage and online backup provider Backblaze has removed Facebook tracking code (also known as an advertising pixel) accidentally added to web UI pages only accessible to logged-in customers. The tracking code was inadvertently added with a new Facebook advertising campaign that started on March 8. The code collected file and folder metadata such as file names, sizes, and dates and uploaded it to Facebook’s servers. No account info or user account info was sent to Facebook while the code was active on signed-in pages.
Source: https://www.bleepingcomputer.com/news/security/backblaze-mistakenly-shared-backup-metadata-with-facebook/