Safari blocked plug-in

macOS Big Sur 11

Plug-ins

“Learn more

Safari no longer supports most web plug-ins. To load webpages more quickly, save energy, and strengthen security, Safari is optimized for content that uses the HTML5 web standard, which doesn't require a plug-in. To enhance and customize your browsing experience, use Safari extensions instead of web plug-ins.”

https://support.apple.com/en-us/HT203051

Is this about signing into a financial website?

It depends on the version of macOS installed on your Mac.

Please let's know the version please.

Newer version of macOS don't use plug-ins.

Upgrade your system.

Upgrade macOS  to macOS Big Sur 11

For instructions:

https://support.apple.com/en-us/HT201475