The Fastly Security Research team has built and deployed a rule to protect customers against the recently announced Microsoft Exchange Server vulnerabilities. Signal Sciences WAF customers have these custom rules available in the console under "Templated Rules". We strongly suggest that customers using Signal Sciences in front of their Microsoft Exchange servers enable these rules as soon as possible and configure them to block requests if the signal is observed. Additionally, follow all guidance from Microsoft to patch affected systems. The vulnerabilities in question are actively being exploited globally and have severe impact.