Methods with the AllowPartiallyTrustedCallersAttribute that call methods without that attribute might unintentionally expose ...

Methods with the AllowPartiallyTrustedCallersAttribute that call methods without that attribute might unintentionally expose functionality to partially trusted code. When a method has the AllowPartiallyTrustedCallersAttribute set, it is callable by partially trusted code. If it in turn calls methods without the attribute, a partially trusted caller is, in effect, being allowed to execute code that requires full trust. Depending on what full trust code is called and what parameter values are passed through from the partially trusted caller, malicious code might be able to exploit this security weakness.