How to Inject jQuery with Chrome in Developer Console?

NOTE: I believe this to be a legitimate question of the type that is welcomed on Stack Overflow. I posted a similar question in late October and it was downvoted and subsequently deleted by the community user. I can’t find the original post, so I’m posting again with modifications to hopefully avoid the downvotes, or at the very least get the common courtesy of a comment explaining why the downvote.

THE ISSUE

I used to be able to (locally) use either of the following two Chrome extensions to easily inject jQuery into pages that didn’t already have jQuery, and that I didn’t own (client-side) to experiment with design changes, development modifications, and real-time troubleshooting:

Unfortunately, now because of what appears to be the newest craze in preventing “XSS” (cross-site scripting), those plugins no longer work. There may be a noble purpose behind these changes, and I’m just trying to understand WHAT changed. I think it has something to do with “content security policy“, which I’ve only recently heard of and have very little knowledge of.

I first learned about XSS as a browser issue in 2011, however, XSS prevention measures had never prevented me from doing local development before. I’ve been searching for a modern (late 2017) solution, to no avail.

I’m not sure where to go from here.

WHAT I’VE TRIED THAT HASN’T WORKED

Here are plugins I tried (which used to work until about 6 months ago) that no longer work for me:

  1. jQuery in Console (Plugin)
  2. jQuery Inject (Plugin)
  3. jQuery Injector (Plugin)
  4. GitHub – bluerabbit/jquery-inject: jQuery-inject(Chrome extension)

Here are some of the many links I encountered that offer solutions which no longer work:

This last one also looks promising, but I haven’t tried it yet:

MY QUESTIONS

  1. How can I inject jQuery (using Chrome Developer Console) into a webpage that doesn’t use jQuery?

  2. Did something change in the browser/JavaScript/programming world significantly enough in 2017 that if a person knew about this particular change or phenomena it would easily explain why the above plugins no longer work?

  3. Why don’t the above plugins work? Did ALL the browser companies universally roll out some major change this year?

Any help is appreciated.

(P.S.: Ive done my best to be thorough, but concise. Please let me know if anything needs clarification and please leave a comment if you downvote this for any reason explaining why. Thanks in advance.)