Apple

They still intended to start scanning your photos and that is worrying.

They wanted to scan photos stored in iCloud. Apple has an entirely legitimate interest in not storing CSAM on their servers. Instead of doing it like every other photo service does, which scans all of your photos on the server, they created a complex privacy-preserving method to do an initial scan on device as part of the upload process and, through the magic of math, these would only get matched as CSAM on the server if they were confident (one in a trillion false-positives) you were uploading literally dozens of CSAM images, at which point they'd then have a person verify to make absolutely certain, and then finally report your crime.

The system would do the seemingly impossible of preserving the privacy of literally everybody except the people that everyone agrees don't deserve it. If you didn't upload a bunch of CSAM, Apple itself would legitimately never scan your images. The scan happened on device and the match happened in the cloud, and only if there were a enough matches to guarantee confidence. It's honestly brilliant but people freaked out after a relentless FUD campaign, including from people and organizations who absolutely should know better.