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Bug reports: Captchas don't show up

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    • CommentAuthorEmil J
    • CommentTimeMar 8th 2011
     

    A couple of times I've been asked to enter a Captcha when posting on MO. The thing is, it never works properly: there is no actual Captcha to be found anywhere on the page. Here is a screenshot:

    screenshot of a CAPTCHA request

    I only managed to get the posts through by reloading the original question and retyping the answer, which I suppose proves I'm not a robot indeed, but doesn't seem to be the intended purpose of a Captcha. The browser is Firefox 3.5.5, and if relevant, JavaScript is not disabled for MO, anything else seems to be working on the site.

    • CommentAuthorMariano
    • CommentTimeMar 8th 2011
     

    Maybe the test has become more lenient with time and now will accept simply clicking on the «I'm a human» button as a proof of humanity?

  3.  

    Has anyone else experienced this? This seems like the sort of critical bug we should report upstream.

    • CommentAuthorEmil J
    • CommentTimeMar 8th 2011
     

    @Mariano: it will not, I tried that of course.

  5.  

    We may want to try to figure out whether this is a rendering problem or a problem that the server is not sending the Captcha. Some minimal diagnosis will probably help upstream sort out what is wrong.

    @Emil J: if you know any HTML/javascript, can you look at the source of the captcha page the next time it shows up? (In firefox hit Ctrl-U or click on View, then Page Source.) If not, you may want to send it (via e-mail) to someone who knows what they are looking for. (I'd volunteer, you can find my e-mail on my user profile on the main site, but you should also get also another pair of eyes to look at it.)

    • CommentAuthorjc
    • CommentTimeMar 8th 2011
     

    @Emil J: It looks like you're using the AdBlock Plus extension. On the off-chance that this might be what's happening, have you checked that a runaway filter isn't blocking the captcha image?

    • CommentAuthorEmil J
    • CommentTimeMar 9th 2011
     

    @Willie Wong and jc: thanks for suggestions, I'll try to investigate it the next time it happens.

    • CommentAuthorJason
    • CommentTimeMar 9th 2011
     
    I think if you hit the back button when the captcha comes up and then hit the forward button, your question or answer will be posted. I did this once and it worked, but it may have been because I had already submitted the captcha first and did this after my request had stalled or been dropped.
    • CommentAuthorEmil J
    • CommentTimeApr 1st 2011
     

    Problem solved: it turns out it was not blocked by AdBlock, but by NoScript. The counterintuitive catch is that the script displaying the captcha is not served from mathoverflow.net or any other expected place, but from www.google.com (disguised by the redirect api.recaptcha.net), and I have blocked javascript on Google for some reason. (I saved the source if needed.)

  10.  

    Jason: I don't think that works. Because I so often have trouble reading the stupid captchas, I very often hit the back button and either hit forward or hit the Post button to refresh the captcha, sometimes repeatedly until I can finally decipher it.

    • CommentAuthorJason
    • CommentTimeApr 1st 2011
     
    Todd: I think you're right, and I've also refreshed the captcha a number of times to try to get to one that looks somewhat readable. It probably worked that time because it likely had accepted my submission despite the fact that the page wasn't loading. But I don't always have to enter a captcha to post a question or answer. I haven't kept track of this, but do you only have to do this every 3 or so posts?
  12.  

    Jason, I haven't tried to track how frequently the captcha calls, but one in every 3 or 4 posts sounds roughly correct.

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