It happens regardless of whether I temporarily trust all scripts on the page or not. After several minutes the warning will clear. Clicking the button [Temporarily Disable Extension on Page] may allow the page <https://secure.comed.com/Pages/Login.as ... Error=true> to show, which may trigger another yellow bar.A script in the extension "NoScript" is causing Firefox to slow down. Learn more. [Temporarily Disable Extension on Page] [Stop It] [Wait]
Logging in from Chrome works normally.
Using Firefox 61.0.2 (64-bit) on Windows 10 Pro 1803.
Also running the 1Password extension, version 188.8.131.52.