Takayuki Miyoshi

Really Simple CAPTCHA does not work alone and is intended to work with other plugins. It is originally created for <a href="https://contactform7.com/" rel="nofollow ugc">Contact Form 7</a>, however, you can use it with your own plugin.
Note: This product is “really simple” as its name suggests, i.e., it is not strongly secure. If you need perfect security, you should try other solutions.
<h4>How does it work?</h4>
Really Simple CAPTCHA does not use PHP “Sessions” for storing states, unlike many other PHP CAPTCHA solutions, but stores them as temporary files. This allows you to embed it into WordPress without worrying about conflicts.
When you generate a CAPTCHA, Really Simple CAPTCHA creates two files for it; one is an image file of CAPTCHA, and the other is a text file which stores the correct answer to the CAPTCHA.
The two files have the same (random) prefix in their file names, for example, “a7hk3ux8p.png” and “a7hk3ux8p.txt.” In this case, for example, when the respondent answers “K5GF” as an answer to the “a7hk3ux8p.png” image, then Really Simple CAPTCHA calculates hash of “K5GF” and tests it against the hash stored in the “a7hk3ux8p.txt” file. If the two match, the answer is confirmed as correct.
<h4>How to use with your plugin</h4>
Note: Below are instructions for plugin developers.
First, create an instance of ReallySimpleCaptcha class:
<pre><code>$captcha_instance = new ReallySimpleCaptcha();
</code></pre>
You can change the instance variables as you wish.
<pre><code>// Change the background color of CAPTCHA image to black
$captcha_instance->bg = array( 0, 0, 0 );
</code></pre>
See really-simple-captcha.php if you are interested in other variables.
Generate a random word for CAPTCHA.
<pre><code>$word = $captcha_instance->generate_random_word();
</code></pre>
Generate an image file and a corresponding text file in the temporary directory.
<pre><code>$prefix = wp_rand();
$captcha_instance->generate_image( $prefix, $word );
</code></pre>
Then, show the image and get an answer from respondent.
Check the correctness of the answer.
<pre><code>$correct = $captcha_instance->check( $prefix, $the_answer_from_respondent );
</code></pre>
If the $correct is true, go ahead. Otherwise, block the respondent — as it would appear not to be human.
And last, remove the temporary image and text files, as they are no longer in use.
<pre><code>$captcha_instance->remove( $prefix );
</code></pre>
That’s all.
If you wish to see a live sample of this, you can try <a href="https://contactform7.com/captcha/" rel="nofollow ugc">Contact Form 7</a>.

Really Simple CAPTCHA

Needed this for an installation with custom forms. I used the plugin developers instructions and was able to make a fully custom implementation based on server side validation within 30 minutes. No more spam bots misusing the forms. Thank you!

Great work - easy to implement

Really Simple CAPTCHA is a CAPTCHA module intended to be called from other plugins. It is originally created for my Contact Form 7 plugin.

Freemius

Silkalns

WP Chill

patrickposner

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Passster offers three protection modes to cover every use case you may think of when it comes to password protecting your WordPress website.
<iframe loading="lazy" title="How to protect a page with Passster" width="750" height="422" src="https://www.youtube.com/embed/kjYklVLVFD8?list=PLM2tOjfhVrZdo_H26CV2I-UfdqpDWxo3D" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture; web-share" referrerpolicy="strict-origin-when-cross-origin" allowfullscreen></iframe>
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<h3>Documentation</h3>
Learn more about this plugin <a href="https://passster.com/kb/" rel="nofollow ugc">in our official documentation</a>
<h3>Support</h3>
<ul>
<li>Free users: <a href="https://wordpress.org/support/plugin/content-protector/" rel="ugc">Ask in our forum</a></li>
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</ul>

Passster – Password Protect Pages and Content


I'm not sure that updating the plugin is the only cause, but it is a cause of this problem: the correct password ceases to unlock the content after an update and says "security check failed" or something when attempting to authenticate.  This causes a periodic freak-out of my customer.  To fix it I have to add and take away the whole-page lock...I think...  It's hard to pinpoint what I actually do that makes it start working again.


Periodically doesn't unlock. Buggy

Password Protect Pages, Posts & Content in WordPress

Really Simple CAPTCHA vs Passster – Password Protect Pages and Content