Problems with Javascript - toString()

Since AR 11.0.11, there is a problem in our Javascript:

var aebPDFXFALib = new Object();

aebPDFXFALib.version = "1.0";

aebPDFXFALib.build = "63";

aebPDFXFALib.toString = function toString() {

return "aebPDFXFALib " + this.version + "." + this.build;

};

The expression aebPDFXFALib.toString() returned "aebPDFXFALib 1.0.63", but since AR 11.0.11 it returns "[object Object]".

I solved it by replacing the overridden toString() with a custom function asString(), but it ruined our application and lot of our users are upset.

What is the reason for such behavior?