Hi @nko
Here is the step by step detail
I have created a block for bootstrap tabs.
1. I have created a code editor field for adding custom attribute in the tab link
see screenshot https://prnt.sc/-drtr_EKCYb8
You can see that I have kept a code editor field “Nav Link Custom Attribute” , whos value I have kept “aria-selected=”true”
2. Now I when check the source code of the page where I used this custom block. I see this in source code , see this screenshot https://i.ibb.co/56HW50b/Image-1.png
So you can see that instead of double quote its showing converted " HTML entity.
This is making the quote invalid.This is happening with single quotation mark also, It is changed to '