CoacoaPods trunk RCE in email verification system rfc-822

trunk.cocoapods.org is the authentication server for the CoacoaPods dependency manager. The part of trunk which verifies whether a user has a real email address on signup used a rfc-822 library which executes a shell command to validate the email domain MX records validity. It works via an DNS MX. This lookup could be manipulated to also execute a command on the trunk server, effectively giving root access to the server and the infrastructure. This issue was patched server-side with commit 001cc3a430e75a16307f5fd6cdff1363ad2f40f3 in September 2023. This RCE triggered a full user-session reset, as an attacker could have used this method to write to any Podspec in trunk.