This is an official PlotSquared addon which adds a marker around claimed PlotSquared plots in the dynmap interface. A simple mouseover will show more detailed information including:
The download is available at Modrinth.
This addon requires PlotSquared and Dynmap to be installed. You can get them below:
Support is available on discord server. If you encounter an issue or want to add a feature, you are welcome to open an issue or raise a pull request.