Regex to find a specific string that is not in a HTML attribute

My case is: I have a string with HTML elements:

<a href="something+specific_string" title="testing">This is a text and "specific_string"</a>

I need a Regex to match only the one that is not in a HTML attribute.

This is my current Regex, it works but it gives a false positive when the string is wrapped by double quotes

((?!"[ws]*)specific_string(?![ws]*"))

I have tried the following Regex:

((?!"[ws]*)specific_string(?![ws]*"))

It works but it gives a false positive when the string is wrapped by double quotes