Cylon LEDs for new tabs on just a few hosts

[bertd2]

I've been having issues with Firefox for quite a while, and recently isolated the issue to NoScript. Firefox 82 on Linux, all other extensions disabled. Unfortunately, the site that reproduces the issue 100% of the time is company internal, so I'm looking for troubleshooting tips rather than a solution, even though I've seen sites like mail.google.com be affected.

If I open a new tab, and navigate to the site in question by clicking a tile in the Top Sites screen, the tab shows the "Cylon LED" animation that suggests it's connecting. The URL bar remains blank (showing the grey "Search with Google or enter address" hint). It's as if nothing was ever selected. If I first navigate somewhere else, say, google.com, and then type the problematic address in the URL bar, I see Cylon LED's. I sometimes even see reference to "Waiting for google.com" or whatever site was in the Tab previously. If I disable NoScript, the problem disappears entirely. So it seems that NoScript, somehow, interferes with Firefox really early on in the process of connecting to a web site. If I click the NoScript Icon, it refers to the old content of the tab, or if it's a new tab, I see the "This is a privileged page" message.

It's been going on for quite a while now, so it's not a Firefox 82 regression. I sometimes see it for every tab after restarting Firefox with a saved session, but for this site the issue is persistent.

Is there any way to debug this issue?

[bertd2]

Forgot to mention: the problem goes away if I disable "Sanitize cross-site suspicious requests". It may well be related to item 4.2 from the FAQ, but I would expect the NoScript menu to show the XSS attempt if that's the cause. Rather, NoScript refers to the old page and doesn't show anything about any attempted XSS.

As a side note, item 4.2 seems to refer to NoScript Classic's UI. Is there a seperate FAQ for the Quantum version of NoScript?

[Giorgio Maone]

Could you try about:debugging > "This Firefox", find NoScript among the extensions and press "Inpsect"?
Then select the "Console" tab, clear it, try to reproduce this issue and watch for any error message.