Kris Zyp kriszyp at xucia.com
Tue Sep 11 07:56:16 PDT 2007

Is __proto__ somehow a new security threat? __proto__ has been around for 
ages in SM/FF and not only that, but it has been there in the more hazardous 
writable form. I just wanted it be actually included in the spec. Or is 
there some new functionality in ES4 that will somehow interact with 
__proto__ to introduce a security threat?
----- Original Message ----- 
From: "Lars T Hansen" <lth at acm.org>
To: "Kris Zyp" <kriszyp at xucia.com>
Cc: "Brendan Eich" <brendan at mozilla.org>; "liorean" <liorean at gmail.com>; 
<es4-discuss at mozilla.org>
Sent: Tuesday, September 11, 2007 2:34 AM
Subject: Re: __proto__

> On the one hand, __proto__ is another potential security hole, and it
> prevents implementations from sharing prototype objects among multiple
> documents -- the link may be read-only but the object isn't.  Function
> B called from function A with object O may hack O.__proto__ and A can
> do nothing about it; suddenly all O-like objects in the system act
> differently.
> On the other hand, Constructor.prototype is generally available for
> any Constructor, so it's hard to see what the real damage is -- it's
> not obviously worse than some other aspects of the language.
> On the third hand, some implementations may have specialized objects
> for which no Constructor is available and for whom keeping
> [[Prototype]] unavailable is desirable.  Similarly, some toolkits may
> have private prototype objects that are not available to client code
> because the constructor is hidden in a lexical scope (ES3) or
> package/namespace (ES4).
> Introspection is great, but it assumes a lot about how trust works in
> the environment.
> --lars
> On 9/11/07, Kris Zyp <kriszyp at xucia.com> wrote:
>> > The alternative above would standardize read-only __proto__, which 
>> > would
>> > make that property no longer implementation-specific. But of  course we
>> > have no proposal to do that.
>> I realize this wasn't really the main subject... but could the __proto__
>> property be defined in the spec (as readonly)? I would love to see that
>> property standardized.
>> Kris
>> _______________________________________________
>> Es4-discuss mailing list
>> Es4-discuss at mozilla.org
>> https://mail.mozilla.org/listinfo/es4-discuss

More information about the Es4-discuss mailing list