https://www.techradar.com/news/macos-quick-look-exploit-could-reveal-all-your-encrypted-data

Quick Look is one of macOS’s most convenient features, but one developer has proven it’s also extremely vulnerable to hacking.

Apple's Quick Look mechanism generates and caches thumbnails of files, images, folders and other data to give users fast and easy access. That’s generally what Quick Look does with all your files, but a security researcher named Wojciech Regula realized the feature is doing the same thing with all your encrypted data and saves those said thumbnails to an unencrypted location.