It's not really any surprise that templates (or CSS) could be Turing complete, as all the lambda() function does is the same thing a template does - replacing the macros in a template with an argument.
This is actually an important lesson that is often missed: if the app you're writing gives the anonymous users any kind of find/replace macro capability, you're giving them a fully Turing complete language (though it's probably not easy, but that rarely stops anyone) and all the potential problems that can bring.
Comments
It's not really any surprise that templates (or CSS) could be Turing complete, as all the lambda() function does is the same thing a template does - replacing the macros in a template with an argument.
This is actually an important lesson that is often missed: if the app you're writing gives the anonymous users any kind of find/replace macro capability, you're giving them a fully Turing complete language (though it's probably not easy, but that rarely stops anyone) and all the potential problems that can bring.