https://www.bleepingcomputer.com/news/security/an-up-to-date-browser-should-keep-users-safe-from-most-exploit-kits/

The times when exploit kits (EKs) were known to be the breeding ground of new zero-days is long gone, and most EKs nowadays live off older vulnerabilities, meaning that keeping your browser, OS, and Flash Player up-to-date is enough to safeguard you from today's top web-based threats.

Exploit kits are web apps developed by malware authors. Crooks lure users on malicious URLs hosting an exploit kit, which uses a known vulnerability to infect the user with malware.