On 2026-10-21, OpenJDK announced a significant vulnerability (CVE-2026-91403) affecting various JDK versions due to compromised CA certificates. Users of JDK versions 8, 11, 17, 21, 25, and 27 need to update their JDKs and can temporarily block the compromised certificates to mitigate the issue. The post provides detailed steps for checking vulnerability and updating certificates.