What does issue 11290 mean to the security of my website

What does issue 11290 mean to the security of my website

Hello,

I know ticket 11290 is very old and fixed a long time ago. Thanks for that.
I plan to upgrade my jQuery as fast as I can.

Using the Retire.js Chrome plugin I get a warning that the jQuery 1.8.3 I included is vulnerable to 'Selector interpreted as HTML'

1) Do I need to be using a special selector feature of jQuery like using a < in my selector for this bug to be a security issue ? 
2) Should I be worried about the overall security of my website ?

(I have a website that is only accessible via https.
It does not load any content from other sources. So all content is on the local webserver.)

thanks,
Richard.