Do I need a security update?

Some users try 'Safe' mode, starting up Mac; then let it run about 10+ minutes.

You may need to see if 'Big Sur macOS 11.x' may be useful to advance. It's stabile.

..This would install after Catalina, in progressive order..

Even if nothing else is done in Safe start mode, I've left it sit and digest what

it may have found, get a coffee; etc. No rush. Then go back, & exit Safe mode

• How to use safe mode on your Mac - Apple Support

//support.apple.com/en-us/HT201262

(Can be more helpful, 'if one attempts to install the update' ~ with Mac in 'Safe' mode.)

~ You can "Exit" easily enough, simply set it to Restart. ~ And let it go.

"Safe mode prevents your Mac from loading certain software as it starts

up, including login items, system extensions not required by macOS, and

fonts not installed by macOS. It also does a basic check of your startup

disk, similar to using First Aid in Disk Utility."

"And it deletes some system caches, including font caches and the kernel

cache, which are automatically created again as needed."

One also may try to start up into Recovery, so the macOS Recovery partition

used as 'repair disk'; to choose the startup partition, from top, as main drive.

• Apple silicon: See Use macOS Recovery on a Mac with Apple silicon.
• Intel: See Use macOS Recovery on an Intel-based Mac.

Depending on which architecture your Mac system has (Silicon or Intel).

Big Sur is worth a try, and some marginal Macs top-out there.

"Safari uses these links to find the old installers in the App Store. After you

download the installer from the App Store, the installer opens automatically.

• macOS Big Sur

macappstores://apps.apple.com/us/app/macos-big-sur/id1526878132?mt=12

Can upgrade Catalina, Mojave, High Sierra, Sierra, El Capitan, Yosemite, Mavericks"

(If unworkable here, [see article where these are] + instructions, above)

Perhaps try an older than Monterey version as 'step up' before attempting Monterey 12.x

• How to get old versions of macOS - Apple Support

//support.apple.com/en-us/HT211683

Suggestions on past attempt to help other users, include upgrades to Mojave 10.14.6,

or perhaps Catalina 10.15.7. Some Macs won't like versions past Big Sur 11.x. Depends

on the configuration and preparation, before those may work without issues. Safari

does not need update to access the Support site shown above or download anything.

• How to upgrade to macOS Monterey - Apple Support

//support.apple.com/en-us/HT212735

There was an update added for Safari in both Big Sur & Catalina recently.

[And Monterey: still been problematic to some who upgraded past Big Sur.]

A Safari 15.6.1 update is available for Big Sur :

Apple security updates - Apple Support

About the security content of Safari 15.6.1 - Apple Support

This is partially why I suggest Big Sur w/ linked 'get download' from

the get older macOS upgrades; using safari was reasonably attuned.

For certain macOS configuration builds (software/hardware)

this remains better path; & perhaps last, Big Sur; as upgrade.

It's always a good idea to keep macOS updated: Update macOS on Mac - Apple Support.

Be sure to follow all those instructions, from Step 1 on down.