Alas, doing that would be detectable from the webpage. So from my 
perspective, its a no-go.

- Blair




On 12/5/09 10:12 AM, Heather wrote:
>
> Here is an interesting idea from someone on Get Satisfaction for one
> way this feature could be implemented.
>
> http://getsatisfaction.com/mozilla/topics/command_subscription_page_feature_to_warn_users_to_install_ubiquity
>
>
> On May 8, 4:46 pm, Blair McBride<[email protected]>  wrote:
>> Great info and links - thanks!
>>
>> I think this is an important topic that needs to be considered when
>> adding code that somehow touches content-space. Thankfully, there have
>> been some really smart people looking into this already, so Ubiquity
>> (and other addons) can learn from previous mistakes and research.
>>
>> It also shows that while these type of information leaks are getting
>> fixed on the Firefox platform (eg, chrome:// URLs are no longer
>> accessable unless whitelisted), its often up to extension authors to do
>> things sensibly and with forethought.
>>
>> Whether or not this type of leak can be used malliciously or not is
>> beside the point - if its not explicitly wanted (and expected) by the
>> user, then its a security bug that needs fixing.
>>
>> - Blair
>>
>> On 8/5/09 4:30 PM, esquifit wrote:
>>
>>> There was some talk about this topic some time ago, see the links
>>> below.  I don't know how vulnerable Firefox is these days.  The same
>>> question arose repeatedly in the context of the Greasemonkey extension.
>>> The GM developers eventually implemented some protection measures that
>>> (I think) are now somehow handled by Firefox itself.   Anthony
>>> Lieuallen's Karma Blocker extension [1] was also very helpful against
>>> this vulnerability.
>>
>>> [1]https://addons.mozilla.org/en-US/firefox/addon/5230
>>
>>> There were essentially two approaches:
>>> 1) When a message bar is displayed as a result of a script being
>>> installed/discovered, the page can detect the vertical displacement
>>> caused by the bar. For example a page could include the<link>  tag
>>> pointing to some (possible non existent) ubiuity script and check for
>>> the vertical shift caused by the Ubiquity bar prompting for installation.
>>> 2) Including a extension's chrome:// image resource from the web page.
>>> Depending on whether the extension was installed or not, the included
>>> image would have length 0 or greater than 0 and would thus affect the
>>> width of some other element in the page.  This could be measured by
>>> javascript code. I think newer versions of Firefox disallow inclusion of
>>> chrome:// images from web content.
>>
>>> Here some interesting links:
>>
>>> Detecting FireFox Extentions ha.ckers.org<http://ha.ckers.org>  web
>>> application security lab
>>> http://ha.ckers.org/blog/20060823/detecting-firefox-extentions/
>>
>>> Jeremiah Grossman: I know what you've got (Firefox Extensions)
>>> http://jeremiahgrossman.blogspot.com/2006/08/i-know-what-youve-got-fi...
>>
>>> Greasemonkey Detect
>>> http://wearehugh.com/public/2006/07/detect-greasemonkey.html
>>
>>> Greasemonkey Detectable? - greasemonkey-users | Grups de Google
>>> http://groups.google.com/group/greasemonkey-users/browse_thread/threa...
>>> <http://groups.google.com/group/greasemonkey-users/browse_thread/threa...>
>>
>>> On Sat, May 9, 2009 at 1:05 AM, Blair McBride<[email protected]
>>> <mailto:[email protected]>>  wrote:
>>
>>>      This would be a security bug if it were possible - it should never be
>>>      possible for web content to detect which extensions a user is running.
>>
>>>      - Blair
>>
>>>      On 4/5/09 1:42 PM, Alphawolf wrote:
>>
>>>       >  Hey there,
>>
>>>       >  is it possible to check with javascript if Ubiquity is installed 
>>> in a
>>>       >  user's Firefox? I'd like to display some install instructions to
>>>      those
>>>       >  only who have it installed already.
>>
>>>       >  Regards,
>>>       >  Oliver
> >

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