Strange red underline (maybe a bug)

Hello, I'm working on an archives page (main category url) but the text of my custom post types appears with a strange red underline, it's similar to the red underline of a text editor to signal a misspelling (like word or libreoffice)

I've tried inspecting the element to see if I can find why or where that style is applied but nothing shows up. I think it may be something in the theme itself

What could it be? I am working with toolset by the way