Support » Plugins » [Plugin: SI CAPTCHA for WordPress] Spammers bypassed CAPTCHA registration system

  • Good day.

    I’ve used SI CAPTCHA plugin since a month ago with my website and it works well until yesterday. In last 24 hours my website has been hit by spammer accounts. Surprisingly the spammers managed to bypass SI CAPTCHA input during registration. Is there any way to block spammers from registering?


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    I recommend using Akismet at the same time. Make sure you have Akismet enabled and the Akismet key registered.

    Reports of this are rare, never had it happen on my servers.
    The captcha is not too weak. You may be targeted with human spammers.
    There are captcha farm services that use real humans to manually enter the spam. The labor is ridiculously cheap.

    Make sure there are no other plugins causing this:
    Maybe another plugin is conflicting.
    Do this as a test: (may take a long time to verify)
    Temporarily disable all your other plugins.
    Does it work now? If yes, enable the plugins one by one to determine
    which one conflicts. Which plugin was causing it?


    Hi Mike,

    Juz Soze Ya Noze :o)

    I have been running SI CAPTCHA on …. hmmm let’s see now9 of my own blogs and well, I lost count of client blogs and SI CAPTCHA works for me FIRST TIME EVERY TIME and with Askimet I’ve had ZERO PROBLEMS – EVER!

    I’ve donated way back, but will be again soon (gotta get over the new PC expense).

    I can’t imagine why so many folks have problems with it. Maybe I don’t because I do installs through “Simple Scripts” hosted on “HostMonster”.

    Anyhoo ….. thanks again for all your hard work.

    I’m back at it and Dead Into It,

    Mike C

    Hi Mike.

    I don’t know if it’s ‘humans’ from a captcha farm, but the posts seem to be gibberish and there is no actual site at the URL so I’m not sure why they would do that. It’s different IPs but the same format, and they come in like 5 at a time. The first couple of IPs I checked all show up on stopforumspam[dot]com.

    When I manually test my site myself the captcha seems to be totally working so I don’t get it – if it’s manual spammers I don’t understand how the posts could benefit them.

    Sorry for the spam, but here are some examples if that helps to give you an idea.

    Author : mokjwzqd (IP: ,
    E-mail :
    URL :
    Whois :
    42M4CZ pgezzxrjvldh, [url=]eddlnunhhmub[/url], [link=]ptbplfwivtnj[/link],

    Author : ezefkkpvtu (IP: ,
    E-mail :
    URL :
    Whois :
    gvy4fK fqhfpbskzkdd, [url=]dikfncwixhro[/url], [link=]wmhxzznshmpp[/link],

    Moderator Ipstenu (Mika Epstein)


    🏳️‍🌈 Halfelf Rogue & Plugin Review Team Rep

    It could be a bot learning how to break captcha.

    Yeah, I just started getting this problem today. Received massive amounts of spam and it was all gibberish oddball unlinkable crap. I knocked the SI CAPTCHA up to high and limited commenting to only 7 days on WP where thereafter it will close the ability to comment since the bot was tracking back into posts from over 6 months ago.

    Keeping my fingers crossed to see if that helps.

    kaotik, make sure the only other security plugin you have is Akismet. See my 1st reply to this post.
    Akismet is the only other anti-spam plugin approved for use with SI CAPTCHA Anti-Spam, others can simply break stuff.
    If another security plugin is combined(not Akismet), the captcha may not work.

    I’m getting the same basic signature that Bradleyhu posted with lots of randomish gibbersh words. It all started about 24 hours ago.

    I’ve poured through my server logs and every time the IP address comes in directly with a HTTP POST to wp-comments-post.php. - - [17/Mar/2011:15:49:39 -0700] "POST /blog/wp-comments-post.php HTTP/1.1" 302 854 "" "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1)"

    Of particular note is that they are getting code HTTP status 302, and not 200 as I’d expect.

    They are not human posts since they are never accessing the page to fetch the captha image. Thus, unless it’s some massive distributed bot that’s sharing session context between clients (highly unlikely), there is a vulnerability in the si-captcha that is being exploited.

    I’m getting hits at a rate of 1-2 times per hour, so, I may try to capture some packet traces to see if I can figure out what they are actually submitting.

    Anyone interested in the packet log?


    I am the plugin author. Please contact me here, I will help you.
    Include the WP version and a list of your plugins

    Premium Support Ticket

    Same thing going on here, last 24 hours I’ve been getting bombarded with spam that I never had before, and yes, I use Akismet. Akismet recognizes it as spam of course as well and I don’t let anything auto-post to my blog without moderation anyway.

    The whole reason I use your captcha is because I hate my inbox getting filled up that I have a bunch of emails waiting for moderation and it’s a waste of time to have to go in and spam a bunch of comments. Your plugin has been a dream because I never got any spam, until the last 24 hours.

    Something is bypassing the captcha, and Akismet or not, the purpose of captcha is to block autobots and they’ve found a loophole in your code. 🙁

    To be totally fair, I posted on Mike’s support page, as he requested. I’ve captured a packet log of how the spammers are going about their deed.

    This is the summary of how this 1 instance played out:

    ** Client 1 loads page. Client 1 is using a Canadian IP address.
    ** PHPSESSID is assigned for the session to Client 1.
    ** ~3 seconds later, Client 1 loads captcha image
    ** Client 1 made no other requests that would have been needed to properly render the page
    ** 12 seconds later, Client 2 (happened to have been an IP in Spain) comes in and directly makes an HTTP POST to /wp-comments-post.php with the same PHPSESSID that was given to Client 1 above. The POST contains a captcha code which I presume was correct (I couldn’t validate it due to not knowing what image was presented to client 1). The POST is successful and the comment is accepted.

    I’ll leave it to folks to speculate as to how the captcha code is being derived. But, what I said about a distributed bot that was sharing session context appears to be exactly what is happening. There are some very clever bot herders out there.

    I haven’t heard back from Mike yet, but, it hasn’t been very long either.

    I have shared the packet trace with Mike.

    Just a ‘me too’, starting seeing this today on one of our blogs. Turned the captcha difficulty up to high, let’s see if that helps.


    I have determined that some sites become specifically targeted by a spammer that uses a combination of a bot and human captcha solver.

    I have examined one specific case, thanks to ‘foobert’, where the spammer was trying to post about 30 times a day.

    This is what made the spammer go away: Install WP-spamFree (it can be installed with SI CAPTCHA Anti-Spam and Akismet). Soon the spammer bot goes away.

    My normal advice is to install (SI CAPTCHA Anti-Spam and Akismet) because SI CAPTCHA Anti-Spam will keep most bots away. If your site becomes targeted with one of these aggressive spammer that uses a combination of a bot and human captcha solver, then I recommend installing (SI CAPTCHA Anti-Spam, Akismet, and WP-spamFree) until that bot moves on. You can later deactivate WP-spamFree if you want. ‘foobert’ still uses SI CAPTCHA Anti-Spam because it did block some spam that WP-spamFree alone did not.

    The wp-spamfree recommendation is only temporary, you can use it during a full-on spam attack. After the attack goes away, you can go back to just SI CAPTCHA Anti-Spam and Akismet. Because all 3 plugins would be more than what is usually needed under normal circumstances.

    Dear Mike,
    I’ve a problem: I’m not more be able to login in the administration area of my blog, because captcha code is not recognized (I’ve tried a lot of time…).
    How can I deactivate the plugin to test? :(((

    Thank you very very much 🙂

    spervirt, you must have another plugin conflicting.

    How to quickly log back in to admin:
    You will have to manually delete the plugin so you can log in again:
    FTP to this folder on your server:
    and delete the “si-captcha-for-wordpress” folder
    Now you can log in.

    This will disable the plugin and you can log in again.

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