As noted by @lapcatsoftware and reported by @mjtsai, Apple seems to be hiding a pretty important Safari update if you're still on #MacOS 18 Sequioa. It's there but you need to install it from Terminal. Start with:

softwareupdate -l --include-config-data

Then use the label of the update you want:

softwareupdate -i --include-config-data "Safari26.5SequoiaAuto-26.5"

which will download the update, ask you to close Safari if it's running, then install the update. No computer restart required.