A white square is displayed in the javascript source in the xml file.

Try to disable all custom plugins:

Does it help? 

Try to disable all custom plugins

BUT still

May you show whole IDE window? 

Is it possible to share a sample project where this could be reproduced? 

It would be difficult to give a sample of the project

These sources work with the paid products we use

I'll just attach a sample file

This phenomenon happened after intellij update

https://drive.google.com/file/d/1yb8L7Emod3brIEznxMbM9s8X3UqhVlBV/view?usp=sharing 

Thank you, reproduced that with 2020.3. 

And it has been fixed in 2020.3.1, please update the installation and clear caches (**File | Invalidate caches and Restart**) after that: 

Update is complete  and  installation and clear caches

but  still  

<iframe width="560" height="315" src="https://www.youtube.com/embed/8vvPBkZEJOo" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe>

https://youtu.be/8vvPBkZEJOo

I created bug request to investigate this deeper: https://youtrack.jetbrains.com/issue/IDEA-258483

Feel free to watch it in order to be notified once it has updates. See [this article](https://intellij-support.jetbrains.com/hc/articles/207241135) if you are not familiar with YouTrack.

hi ~    ver 2021.1 EAP    Be resolved  

 BUT JRebel debug failed 

ex) jrebel run 'OK'  

Try changing the ports as shown here: https://i.imgur.com/2I6lwPR.png, https://i.imgur.com/FgWFHab.png.

Veiry with https://docs.microsoft.com/en-us/sysinternals/downloads/tcpview that the port is not already taken by some other app.

See if disabling the antivirus/firewall helps.

Try to run "netsh winsock reset" in the Administrator command line and reboot.