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Re: Vulnerability in CB Captcha for Joomla and Mambo

Define vulnerability here.  I don't think this is one.

Granted I have to apologize that my post was a very tongue in cheek snarky comment regarding the fact that Mr. MustLive appears to be posting up one by one of every web site that he finds with bad captcha implementation. I was outting myself in advance because the captcha on my blog site lets spammers wiggle in. But the spam clean up routine clears it out in a week so at most it's an annoyance to me not a vulnerability. So I know I have this issue, but on my stack of risks to worry about, this not one that keeps me awake at night.

Is it of value to this list to be notified of every single web site out there that has such a captcha deployment? How about we ask Mr. MustLive to post a recap once a month of these types of issues rather than each time he finds a site?

Is this of such a degree of impact to a system's information assurance that this audience has to be informed of each instance?

I have this "vulnerability" on my site. I ignore it for now. I have higher priority risks to deal with, this gets handled by the spam engine on the box.

My implied point is that I think we've already been informed that captcha has weakness and in general isn't an 100% effective gatekeeper.

James Martin wrote:
Dear Susan:

Respectfully, why did you subscribe to Bugtraq? I subscribed to be notified when a vulnerability was found with software that I am using. Just saying.


On Apr 15, 2010, at 2:11 PM, Susan Bradley <sbradcpa@xxxxxxxxxxx> wrote:

Dear Bugtraq.

I am an admin of a site that has Captcha that spam gets through and the CPU sucks.

Honest question -- are you going to post about every site that has lousy captcha? Would it be faster if us admins that have lousy captcha just outted ourselves first?

MustLive wrote:
Hello Bugtraq!

I want to warn you about security vulnerability in plugin CB Captcha
(plug_cbcaptcha) for component Community Builder (com_comprofiler) for
Joomla and Mambo. The posting of this advisory to mailing lists was delayed, because I found that there are two different vulnerable versions of plugin
developed by different authors, so I needed to inform all authors.

Advisory: Vulnerability in CB Captcha for Joomla and Mambo
URL: http://websecurity.com.ua/4087/
Affected products: CB Captcha 1.0.2 and previous versions (developed by
Kotofeich), CB Captcha 2.2 and previous versions (developed by Beat).
17.03.2010 - found vulnerability.
31.03.2010 - disclosed at my site.
01.04.2010 - informed developer of CB Captcha 1.x. And because I found other
version of the plugin by another author, and after checking it later I
informed author of CB Captcha 2.x.
13.04.2010 - additionally informed developers of Community Builder (both
joomlapolis.com and communitybuilder.ru).

This is Insufficient Anti-automation vulnerability.

This plugin is based on captcha script CaptchaSecurityImages.php and I
already reported about vulnerabilities in CaptchaSecurityImages
(http://websecurity.com.ua/4043/). And in plugin plug_cbcaptcha were fixed all Insufficient Anti-automation and Denial of Service vulnerabilities from
original script, except one.

Insufficient Anti-automation:

In the plugin it's possible to bypass captcha with using of session reusing with constant captcha bypass method (http://websecurity.com.ua/1551/), which
was described in project Month of Bugs in Captchas. With using of this
method it's possible to bypass protection by sending the same code of

It can be done at all pages where this plugin is used. In CB Captcha 1.x it's using at registration page, lost password form and lost email form. In CB Captcha 2.x, in addition to before-mentioned forms, it's using at contact form (in the presence of component CB Contact 1.1) and login form (in the
presence of login module of CB 1.2).


The PoC for this Insufficient Anti-automation vulnerability was provided to developers. Everyone who want can create such PoC from exploit provided in
above-mentioned article from MoBiC project.

Best wishes & regards,
Administrator of Websecurity web site