I consider a wide range of web frameworks and most do not mention security as an issue on their sites (e.g. scriptaculous, jQuery, Prototype, Rico)
Does anyone know what is more or less secure than others? (ignoring common security holes that JavaScript uses like XSS)
Considering that websites can return malicious javascript, I would have guessed this in a browser (not before javascript) for security.
qooxdoo claims to be free of memory leaks and also provides a destructor mechanism in its class definitions.
As Javascript says for sandboxing, there should be no security issue in any framework as such. There may only be browser / JS implementation bugs, if any.