Firefox "Did Not Connect: Potential Security Issue" is incomplete.
 

Occasionally when I go to a site Firefox will show the message
"Did Not Connect: Potential Security Issue"
and will offer two choices:Go Back (recommended) and Advanced.

If I click on Advanced, it then offers the option of ignoring the recommendation and continuing on to the dubious site (for some reason this always happens when I go to look at the Washington Post!).

The other day I went to look at a site and the Firefox warning came up, but only partially: the lower part of the website page was showing, and when I clicked on Advanced, apparently the rest of the Firefox window was hidden. Possibly the screenshot will make this clear.

This may well be a page I shouldn't be visiting, but my question is rather, what has happened to the Firefox page, and is there a fix?

I am running the latest Firefox with Linux Mint 19 Cinnamon.
Thanks.

Would be interesting to know what reason the Advanced page cites for blocking that site.

Never seen anything like it.
Addon interfering?
Fake Firefox warning site?

 

It's an iframe.

Right-click and open in new tab and you'll no doubt get the full warning/options.

Why, it is all spelled out in your own screenshot:

Since this is a "https://ww1...." site, what do you expect?

The question was not "why does Firefox not trust this site" but rather, why was the Firefox warning not displaying completely.

I didn't know what an iframe was, but boughtonp's advice seems to work (although my connection has been pitiful lately, so it may be a while before I am sure!

Note that, these days, if that is the worst of my troubles, that means I have very little to complain of!

Thanks all, and be careful.

I always assumed in these cases (which happen to me, too) that part(s) of the page are correctly secured with a valid certificate and thus get displayed, while others are not. Most pages nowadays are puzzled together from multiple sources / servers ... thus my possibly too short post above, sorry.