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Firefox exploit found in the wild

blog.mozilla.org

41–50 of 277 posts

Re: Firefox exploit found in the wild

#41
post #30

Earlier quoted context omitted.

In that case, is the issue actually specific to pdf.js? If it's written entirely in javascript, could this not be exploited some other way? Or does pdf.js have special permissions in this context?

Well, if I recall correctly, pdf.js is an add-on, so it has special permissions, just like any add-on.

Ah-ha. I believe it can also be run embedded in a page (GitHub does so), so it CAN be run without special permissions.

Re: Firefox exploit found in the wild

#43

The lack of additional detail in this very sparse announcement really compromises users' ability to damage control effectively. Would like to know if an installation is vulnerable if: 1) If Applications, PDF is set to "Always ask" 2) Ublock and/or privoxy are used 3) Javascript is disabled 4) pdfjs.previousHandler.alwaysAskBeforeHandling == false 5) pdfjs.disabled == true Also which advertising network and which Russ…

Agreed, I use an ad blocker and have Firefox's PDF viewer disabled and I have no clue if I'm still vulnerable. At a minimum, I'd like to know if disabling the viewer is enough to mitigate the risk, or if popular add-ons like Adblock Plus, NoScript, or Privacy Badger are enough.

Re: Firefox exploit found in the wild

#44

Well, sending some user files to Ukrainian server is a bug. But sending hashes of your downloads to Google [1][2] is a feature, right? 1. https://support.mozilla.org/en-US/kb/how-does-phishing-and-m... 2. https://bugzilla.mozilla.org/show_bug.cgi?id=1138721

How can I disable this.

Re: Firefox exploit found in the wild

#45
I believe using "about:config" and setting "pdfjs.disabled" to "true" will neutralize the vulnerability, at least from the description they gave of it, but confirmation from them to that effect would be appreciated, especially for users stuck on the current (or older) version, as the download page acknowledges some might be:

Note: If you use your Linux distribution's packaged version of Firefox, you will need to wait for an updated package to be released to its package repository

It would be particularly scandalous if they knew that disabling pdfjs would suffice yet refused to mention it because they couldn't bear to see their precious CPU/memory-hogging scribd knockoff no one asked for being disabled by their users, in effect putting their grandiose vision of the browser-as-OS ahead of their users' security.

Re: Firefox exploit found in the wild

#46
post #3

I don't even want my browser to have a 'local file context', is there a way to switch such behavior off entirely until explicit permission is given? All these extra bells and whistles added to browsers to allow websites to pretend they're 'native apps' should require a very large switch to be thrown from 'safe' to 'unsafe' whenever an application requests such a thing. And what a pdf reader has to do with javascript…

Every major browser has a built-in PDF viewer (except maybe Safari? I don't own a mac). Mozilla's is the only one that's written in JS. The rest are proprietary native blobs. There have been security vulnerabilities (significant ones) found in the native PDF viewer blobs before, so given the choice between a same-origin policy breakage in pdf.js and an exploit in a native PDF viewer that can own my entire machine, I'll take pdf.js any day.

Maybe it would be better if browsers didn't have a pdf viewer, though. Then I'd have to manually download it and open it in a viewer to get owned, which is not going to happen with an ad network.

The fact that every major pdf viewer app tries to install a browser plugin doesn't help.

Re: Firefox exploit found in the wild

#47

Well, sending some user files to Ukrainian server is a bug. But sending hashes of your downloads to Google [1][2] is a feature, right? 1. https://support.mozilla.org/en-US/kb/how-does-phishing-and-m... 2. https://bugzilla.mozilla.org/show_bug.cgi?id=1138721

How can I disable this.

https://support.mozilla.org/en-US/kb/how-does-phishing-and-m...

Re: Firefox exploit found in the wild

#48
post #3

I don't even want my browser to have a 'local file context', is there a way to switch such behavior off entirely until explicit permission is given? All these extra bells and whistles added to browsers to allow websites to pretend they're 'native apps' should require a very large switch to be thrown from 'safe' to 'unsafe' whenever an application requests such a thing. And what a pdf reader has to do with javascript…

Run the browser in a container or in a sandboxed environment (kindof like chroot, but note that chroot itself should not be used for security purposes). There may be docker containers with just firefox, if not it's easy to create one. Or use vmware, though that is much more heavyweight than sandboxing or containers.

Wouldn't selinux be enough? Browsers have no business touching files outside of ~/.mozilla or whatever.

Re: Firefox exploit found in the wild

#49

The lack of additional detail in this very sparse announcement really compromises users' ability to damage control effectively. Would like to know if an installation is vulnerable if: 1) If Applications, PDF is set to "Always ask" 2) Ublock and/or privoxy are used 3) Javascript is disabled 4) pdfjs.previousHandler.alwaysAskBeforeHandling == false 5) pdfjs.disabled == true Also which advertising network and which Russ…

Totally agreed. I use a few of those, and I have exempted pdf.js in the past because I would rather use that then native PDF readers on my work laptop, since Adobe Reader/Acrobat is a wonderfully famous vector.

Inquiring minds would like to know.

Re: Firefox exploit found in the wild

#50

Earlier quoted context omitted.

> And what a pdf reader has to do with javascript is a mystery as well. The whole reader is written in Javascript: https://mozilla.github.io/pdf.js/

Oh great. What could possibly go wrong, give javascript access to local storage through some 'hard to trigger' gate. That's just asking for it. Hindsight and all that but still, this is not a good idea. A browser should not use it's own internal language sandboxed for the web to have access to the local system through some loophole. It's only a matter of time before such a loophole becomes an exploit. I wonder if jav…

You're getting old and grumpy, Jacques, before you know it you will start your sentences with "back in the day..." :)

On a more serious note, I guess this is the toll we have to pay for innovation pushing. I can understand the reasoning behind writing everything in JS: it allows you to consolidate a lot of mechanisms in a single platform. Once you have that platform secure, any application you will write will (should?) be secure too.

Too bad that theory and practice are usually not the same, in practice..

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