why [removed] tag in js string is being validated

Question

I have following page

Answer 1

HTML is parsed before and independent from Javascript. The current browser behavior is that, once an open tag is found.

Where the is detected doesn't matter — inside a JS string, a JS comment, a CDATA section, or even HTML comment.

You need to make the string does not look like to the HTML parser. The simplest way is to write <\/script> as in @Daniel's answer.