Q: safari upgrade for mountain lion

It is always best practice to keep your Mac up to date as much as possible. Mountain Lion is way too old an OS to be on if you can upgrade to a newer OS. Same goes for Safari. Such an old version might have tons of security issues that financial services deem too risky to operate under. It's time for an upgrade, mate!

Apple has removed Mavericks, Yosemite and El Capitan from the App Store. Your only option is to upgrade to Sierra.

Try another browser.

Firefox

Opera Browser

SeaMonkey

Waterfox Web browser has just been updated for use with OS X Mountain Lion, also.

https://www.waterfoxproject.org/

https://storage-waterfox.netdna-ssl.com/releases/osx64/installer/Waterfox%2049.0 .2.1%20Setup.dmg