A security patch is a software change that corrects a weakness attackers could exploit. It may arrive through an operating-system update, browser update, app store or vendor updater. A popup on an unrelated website saying "critical update" is not a trustworthy patch channel.
A useful example
Your browser says an update is available. Open its own
About page to check the version and install the update there, then restart if requested. Do not download a file from a banner that claims to be the same update. For a router, use the official firmware function or the manufacturer's verified site.
Know when it is done
Confirm the new version or update status after restart. Some fixes require a reboot before protection takes effect. Automatic updates reduce the delay, but unsupported devices may stop receiving fixes entirely. CISA's
update guidance recommends keeping software current. An update reduces a known risk; it does not certify every part of a device as safe.
Practical distinction
A downloaded update is not necessarily an installed update. Reopen the application's own version page after restart and confirm it reports the new version.
