https://e-mfc.ru/ — website for documentational interoperation between the state and citizens.
100% CPU utilization, or almost 100%, and web browser turns hardly responsive.

Encountering the issue in FireFox 107.0 and 102.5.0esr, both 64-bit.
Chromium seems to work fine.
Without JShelter FireFox works fine on the website.

JShelter Version: 0.11.1
OS: OpenBSD 7.2 amd64
Other extensions that might affect JShelter behaviour: tested with all others off

Popup information (open JShelter popup on affected pages):
Doesn't open for over a minute.
Didn't set any custom options — have kept all defaults.