According to some sources, if the content property is a url it should be wrapped in "url()".
See this example from
https://www.w3schools.com/cssref/pr_gen_content.asp
Code:
<!DOCTYPE html>
<html>
<head>
<style>
p::before {
content: url(w3css.gif);
}
</style>
</head>
<body>
<p>My name is Donald</p>
<p>I live in Ducksburg</p>
</body>
</html>
So if the "url()" wrapper is required for a url in a content property we should be able to restrict on that, right?