Miscellaneous Hacks - Patched Flash Uploader to Fix Known Exploits

UPDATE Dec 2014: 4.2.2 PL2, 4.2.2 PL3 and 4.2.3 core download packages from vBulletin now include this patched version of uploader.swf as standard.

This is a patched version of YUI 2.9.0 uploader.swf as used by vBulletin 4.x for managing multiple file uploads.

An exploit was found in the flash uploader (uploader.swf) file supplied with vBulletin 4.x. This file is part of the Yahoo YUI 2 Library which is end of life and Yahoo have stated that they will not be fixing it. Yahoo recommends that the file is removed as the flash uploader has been deprecated.

vBulletin's recommended fix is to replace the file with an empty file of the same name. If you do this, however, and rely solely on the Ajax uploader you will not be able to select multiple files without further modifications.

This modification is a recompiled version of uploader.swf with the above exploit fixed. An additional potential exploit has also been fixed by disabling a parameter not used by vBulletin.

The YUI source used is provided freely by Yahoo to whom I give full credit.


1) Installation

a) Extract uploader.swf from the .zip file and replace your existing file here:

<forum_root>/clientscript/yui/uploader/assets/uploader.swf

b) Make sure the flash uploader is enabled in the Admin Control Panel

Options -> Message Attachment Options -> Asset Manager - Enable -> Select "Yes, Flash Upload by Default"

c) Make sure you are NOT using remote YUI

vBulletin Options -> Server Settings and Optimization Options

Use Remote YUI set to None

d) You may also need to clear your browser cache and/or vBulletin cache (Maintenance ->Clear system cache) if you have performed the above steps correctly but clicking the Upload button still does nothing.



2) Changes

11th January 2014

The parameter 'allowedDomain' has been sanitised with a REGEX to prevent malicious javascript being passed in a query string.


11th January 2014 v2

Many thanks to FranzBanz (http://www.vbulletin.com/forum/member/449383-franzbanz) for his suggestions

• finding another exploit (using another parameter). Exploit fixed by setting the parameter (not used by vBulletin) to null.
• '-' Character added to allowed characters in allowedDomain

Non-Flash Alternative
Please note that if you would rather avoid using flash altogether an alternative Mod has been released by BirdOPrey5, although there are some compromises/limitations with IE10+.

Asset Manager / Image Upload Fix to upload multiple files like the Flash uploader


DISCLAIMER
I am not a flash developer, I am just another vBulletin customer trying to keep his members happy!
This file is provided free of charge for the benefit of the vBulletin community. You use it at your own risk!


Copyright ? 2013 Yahoo! Inc. All rights reserved.
Redistribution and use of this software in source and binary forms, with or without modification, are permitted provided that the following conditions are met:

Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.

Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.

Neither the name of Yahoo! Inc. nor the names of YUI's contributors may be used to endorse or promote products derived from this software without specific prior written permission of Yahoo! Inc.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

[alexm]

Originally Posted by tom w

Being a paranoid security type, any chance of getting the source code for this replacement file? Since it doesn't come from either Yahoo or VBulletin (for whatever reason) I'm reluctant to trust files from a relatively unknown sources (though it's great people like to help) which could introduce other vulnerabilities that we'd never know about.

I would be happy to share the source with another developer if their suggestions/feedback helps the community as a whole, but how would you know if I've given you the correct source? And, also being a paranoid security type with a busy vB4 forum myself, how do I know you aren't looking for vulnerabilities to exploit yourself?

I think the easy answer is if you understand Flash it's very easy to decompile the SWF yourself and look at the source. That's basically what I did to get it working anyway.

If anyone does find an issue let me know and I'll do my best to incorporate a fix.

[BirdOPrey5]

Originally Posted by tom w

Being a paranoid security type, any chance of getting the source code for this replacement file? Since it doesn't come from either Yahoo or VBulletin (for whatever reason) I'm reluctant to trust files from a relatively unknown sources (though it's great people like to help) which could introduce other vulnerabilities that we'd never know about.

FYI

There are many free flash / swf file decompilers online you can upload the .swf file and get the source yourself.

For example - http://www.showmycode.com

[furnival]

I belatedly upgraded to VB 4.22 and had to reinstall this afterwards. This should be incorporated into the next VB 4 release so that everyone doesn't have to reinstall this once more.

[msnhockey]

I cant seem to get this to select more than 1 image in IE or Chrome with the settings in the instructions and with deleting browser cache. any ideas?

I am using IE 11 and Chrome version 33.0.1750.146

[Zachery]

Originally Posted by furnival

I belatedly upgraded to VB 4.22 and had to reinstall this afterwards. This should be incorporated into the next VB 4 release so that everyone doesn't have to reinstall this once more.

there are no plans to add the flash uploader back, in any form, at this time.

[joeychgo]

Originally Posted by Zachery

there are no plans to add the flash uploader back, in any form, at this time.

Zack, is there any reason to think this fix doesn't solve the problem? If not, then why not add it back with this fix?

[BirdOPrey5]

Originally Posted by joeychgo

Zack, is there any reason to think this fix doesn't solve the problem? If not, then why not add it back with this fix?

Legal reasons...

[Zachery]

Originally Posted by joeychgo

Zack, is there any reason to think this fix doesn't solve the problem? If not, then why not add it back with this fix?

It may solve today's problems, but not tomorrow, or the day after, or the day after.

There have been a long and sordid history with the flash uploader, and YUI's security of flash scripts. The YUI devs themselves have abandoned the script.

We can address the changes with something like relying on the HTML5 constructs of modern browsers instead by adding a simple MULTIPLE line to the input. That'd be the fix we'd go with, without adding another issue into the mix.

[tbworld]

Thanks @Zachery, nice explanation. Always appreciated.

[Reef Man]

It does not wolve the problem. I have 4.2.2