The More You Know, The More You Know You Don’t Know

Google Project Zero’s 2021 Year in Review analyzes a record 58 in-the-wild zero-day vulnerabilities detected and disclosed that year, finding that the increase was driven largely by better detection and disclosure rather than novel attacker techniques; most 0-days were memory corruption bugs reused familiar exploitation patterns, though a few (notably FORCEDENTRY) demonstrated high technical sophistication and real-world impact across browsers, mobile OS kernels, Android drivers, and Exchange Server.