Release Notes for v42.9.3

Fixes

Fixed a graphical glitch on Linux where thin borders appeared past the drop shadows on frameless windows when multiple windows were created. #52772 ^{(Also in 43, 44)}
Fixed a memory leak when creating BrowserWindows. #52893 ^{(Also in 43, 44)}
Fixed an issue on Windows where the app process could fail to exit after app.quit() while a shell.openExternal() or shell.openPath() call was still waiting on a system "Open with" dialog. #52900 ^{(Also in 41, 43, 44)}
Fixed custom V8 snapshots (electron-mksnapshot, and the loadBrowserProcessSpecificV8Snapshot fuse) having no effect in the main process on macOS arm64, Linux x64 and Windows x64. #52876 ^{(Also in 43, 44)}

Backported fix for 524628213. #52869
Reduced idle main-process CPU wakeups caused by Node.js timers and immediates. #52907 ^{(Also in 43, 44)}