https://support.mozilla.org/en-US/kb/firefox-users-windows-7-8-and-81-moving-extended-support

Firefox from Mozilla requires Windows 10, 11 to run for Fx 116.0 and later including Fx 151.0 release and Fx 140.11.0esr.

Firefox 115.39.0esr out on August 19 is the last planned update for the old Firefox 115 ESR unless Mozilla decides before then to extend updates yet again.

You can try to change your Firefox version number to fool the unnamed banking site.

• In a new tab, type or paste about:config (with a colon) in the location (address) bar and press Enter/Return. Click the button accepting the risk.
• In the search box in the page, type or paste forceVersion and pause while the list is filtered
• Double-click the network.http.useragent.forceVersion preference to display an editing field, and change the value to 128 or 140 then press Enter/Return or click the blue check mark button to save the change.