Protecting css from XSS?

Question

XSS

Good day. How can I protect myself from any vulnerabilities when parsing a css file?
I'm parsing a css file from a file, and submitting from a textarea to an html form with syntax highlighting, where it gets executed. Just pasting <script>alert(1)</script>it gives 1. I could use htmlspecialchars, but it will corrupt the css structure and make it invalid.
What can be done in such a case?

Answer 1

php strip_tags. Strips tags from text along with content. (The tags are not checked for validity. Removes everything enclosed in <> </>). In theory, CSS shouldn't hurt.