Apple doesn’t say much about this update:
macOS Catalina 10.15.7 provides important security updates and bug fixes for your Mac.
• Resolves an issue where macOS would not automatically connect to Wi-Fi networks
• Fixes an issue that could prevent files syncing through iCloud Drive
• Addresses a graphic issue that may occur on iMac (Retina 5K, 27-inch, 2020) with Radeon Pro 5700 XT
I guess the next release will be MacOS 11 (X1) “Big Sur” …
*** I always recommend the Combo Updater when available. The Delta patches seem to be unreliable to leftover previous versions (aka band-aiding). The Combo will replace the OS changes throughout.