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@@ -1,5 +1,16 @@
 # Security Policy
 
+## Trust model
+
+PHP_CodeSniffer standards and configuration are not sandboxed.
+
+Rulesets may load and execute PHP code supplied by the analyzed project, including custom sniffs and autoloaded files.
+Repository-local PHPCS configuration should therefore be treated as executable project code.
+
+Running PHP_CodeSniffer against an untrusted or attacker-modifiable checkout must be treated in the same way as running that checkout's tests, build scripts, or other development tooling.
+
+CI environments processing untrusted contributions are responsible for appropriate isolation, including restricting access to credentials, secrets, privileged services, and sensitive network resources.
+
 ## Supported Versions
 
 For all repositories in the PHPCSStandards organisation, the latest patch version of the current major is supported for security updates.