Adblock Plus and (a little) more

Firefox closes ad blocking loopholes · 2007-04-19 00:57 by Wladimir Palant

Adblock Plus has just got a little more useful. Yesterday two patches of mine landed on the Mozilla 1.8 branch which will be used for Firefox What are they good for? They close loopholes that advertisers could use (and some already do use) to initiate requests to their servers without Adblock Plus interfering. One loophole is XMLHttpRequest commonly used by AJAX application, the other are requests created by plugins like Flash — neither of the two went through content policies (meaning Adblock Plus as well) before. I just downloaded the current Mozilla 1.8 nightly and verified that this has changed.

Let’s take the example that brought up this topic originally: Yahoo Maps. The whole user interface including the ads is implemented as one single Flash object. This means that in Firefox you have “all or nothing” choice — either you block the Flash object which effectively locks you out of Yahoo maps or you don’t block anything and have to accept the ads. But if you open the list of blockable items (Ctrl+Shift+B) in Firefox you will see a whole lot more there, lots of addresses with type “other”. That is data requested by the Flash object, some of it displayed and some processed internally. In particular you will see some addresses starting with “”, that’s the data used to display ads. Add the filter “|*” to your list and the ads disappear (I hope to see this filter in EasyList soon).

Note that this might not work correctly in Adblock Plus, you should upgrade to Adblock Plus 0.7.5 (hopefully released tomorrow, release candidate is here). And of course it will not work in Adblock which ignores type “other”. Finally, Yahoo Maps uses browser sniffing that causes it to behave strangely in Firefox nightlies. To “fix” go to about:config, find the preference general.useragent.extra.firefox and replace “BonEcho” by “Firefox”.


Comment [9]

  1. mikko · 2007-04-19 17:55 · #

    thx for your support and great adblock+ development keep up your good work :)

  2. raj · 2007-05-03 08:39 · #

    Adblock plus is what best anybody can get.
    superb work..keep it up
    good luck!!

  3. Bruce · 2007-05-05 01:12 · #

    thanks Wladimir. Still using regular Adblock but am about to try the latest Adblock Plus. Can’t help but notice your continual work and help all over the place with regards to ad-blocking.

    Thanks for improving Firefox with your changes. It’s all above my head but anything to stop the advertisers is fine by me.

    Well done.

  4. Buddy21 · 2007-05-16 12:05 · #


    I use the following,

    Adblock Plus
    general.useragent.extra.firefox = Firefox/

    I still get those flash ads on yahoo maps.

    Reply from Wladimir Palant:

    I think the title of the post already says it – this is only for Firefox which isn’t out yet (there are nightly builds however).

  5. RedSox Fan · 2007-06-03 18:28 · #

    Well, is out now and — thanks to this blog — I think I know why the flash-based gameday audio-video on the MLB websites is now messed up unless I use IE.

  6. ben · 2007-06-24 08:01 · #

    Just use Google Maps. It is the far superior service anyway, and does not use flash. Problem solved.

  7. Adam · 2008-03-22 15:44 · #

    If you use ad blocking software, you are leeching off the free web without giving anything back, and depending on those who do not leech to keep your favorite websites free.

    Reply from Wladimir Palant:

    I think you want to read this article:

    But I agree that Adblock Plus needs to differentiate more – this is work in progress.

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  9. dj · 2008-06-10 01:38 · #

    I hope sites start banning all the idiots that use adblockers.

    You have two choices:

    1. Pay to view the websites.
    2. Let the websites remain free by allowing advertising.

    Somebody has to pay the people who make these sites. It’s either you or the advertisers. Which do you prefer ?

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