US-CERT and cybersecurity firms are warning of a critical vulnerability in the Bourne Again Shell, known as Bash, which is present in most Linux and Unix distributions as well as Mac OS X. Bash is highly prevalent, but very specific conditions need to be in place for it to be exploited. Still, users and administrators are advised to review the Redhat Security Blog for additional details and refer to their respective Linux or Unix-based OS vendor(s) for an appropriate patch. Additional information is available from US-CERT and Threatpost.