I’m getting a Bev-manage-ui download message every time I try to log into Social Security website.

This Discussion described a similar problem and solution: I just updated to OS 11.7 AND Safari Version 16.0 (16614.1.25.9.10, 16614). Now when I try to sign in to SSA.gov I get as far as the pg that requires the phone code, it accepts, opens to blank site and sends an "unknown" doc to downloads. - Apple Community

The solution was found in If Safari on Mac doesn't open a webpage or isn’t working as expected - Apple Support, under Test with a private window:

A website can store cookies, caches, and other data on your Mac, and issues with that data can affect your use of the website. To prevent the website from using that data, view it in a private window. From the menu bar in Safari, choose File > New Private Window, or press Shift-Command-N.



If that works, use the following steps to remove the website's data, including its caches and cookies. The website can then create new data as needed. If it's a website that you sign in to, make sure that you know your sign-in information before continuing.

1. Choose Safari > Preferences, then click Privacy.
2. Click Manage Website Data.
3. Select the affected website from the list shown.
4. Click Remove.
5. Click Done.
6. Open the website again in a non-private browser window.

See if that works for you.