libXext is the historical libX11-based catchall library for the X11 extensions without their own libraries.
No new extensions should be added to this library - it is now instead preferred to make per-extension libraries that can be evolved as needed without breaking compatibility of this core library.
All questions regarding this software should be directed at the Xorg mailing list:
https://lists.x.org/mailman/listinfo/xorg
The primary development code repository can be found at:
https://gitlab.freedesktop.org/xorg/lib/libXext
Please submit bug reports and requests to merge patches there.
For patch submission instructions, see:
https://www.x.org/wiki/Development/Documentation/SubmittingPatches