The vulnerability stems from Safemode's Blankslate class explicitly allowing the 'inspect' method in both instance and class method whitelists. The commit diff shows 'inspect' was removed from both @@allow_instance_methods and @@allow_class_methods arrays in lib/safemode/blankslate.rb. Since Safemode delegates to Rails controllers, calling 'inspect' on these objects would leak sensitive application state. The patch directly addresses this by removing 'inspect' from allowed methods, confirming these were the vulnerable functions.