What JavaScript interpreter does Polkit use to interpret rules.d files?

What JavaScript interpreter does Polkit use to interpret rules.d files? The source code at time of writing links to a defuct Wikipedia heading ["ECMAScript.2C_5th_Edition"](https://gitlab.freedesktop.org/polkit/polkit/blob/8f0ef12901d36d1237a28a9abea509daef873feb/docs/man/polkit.xml#L506) , however that would only be the specification the interpreter is written to, not the specific implementation that is being used to interpret polkit rule files. Knowing what and how a javascript interpreter embeded in an authorization system is used would be nice to declare clearly. to disambiguate details such as where the interpreter is being embedding, what is sharing the runtime, when rules files functions are interpreted, if they are being interpreted asynchronously etc; clearly would be nice too.