Over the last few months a lot of users complained about lots of spam due to using the "form builder" addon. While a lot of new captcha solutions have been integrated by joomshaper, the "Default" option still produces LOTS of spam mails.
Sadly, we have some projects where - due to legal reasons - thrid party captchas are not possible.
I digged into this issue and found out, that the Captcha Answer is integrated as a hidden field in the resulting form. The answer is hashed (md5), but as long as standard numbers are used an attacker can easily find out, what the answer is: By simply comparing the hash values of common answers.
For example, the captcha Answer in the following form is "7", which can be easily determined by reverse-engenieering the MD5-Hash.
....
<input type="hidden" name="captcha_answer" value="8f14e45fceea167a5a36dedd4bea2543">
<input type="hidden" name="captcha_type" value="default">
<div class="sppb-form-check">
....I'm honestly baffled that seemingly no one has determined the core of the problem and the solution was to implement multiple other third party captcha services.
The solution is rather simple - Just use some kind of dynamic salt before hashing the captcha_answer in line 314 and 599 of addons/formbuilder/site.php
Would be great if this can be fixed!
Thanks!
