I am experiencing a problem with the Captcha module 7.x-1.3 version (under Drupal 7.39)

• I don’t use webforms
• My form is a simple Contact form
• My form does not contain any AJAX field
• My form does not contain any file or image upload system
• I configured the captcha Module, giving the good name for the form
  • form_id : xxxxxx_contact_form
  • Challenge type : Image (from module image_captcha)
• In the Configuration (admin/config/development/performance)
  • The page cache for anonymous users is unchecked = NOT ACTIVATED
  • The cache for blocks is unchecked = NOT ACTIVATED

The code of the Captcha for my form is :

$form['xxxxxx_contact_captcha'] = array(   '#title' => t('Vérification'),   '#type' => 'captcha',   '#captcha_type' => 'image_captcha/Image', ); 

When a user is connected the form submission works well without any problem BUT when NO user is connected (= anonymous session), i get the following errors :

• CAPTCHA session reuse attack detected.
• The answer you entered for the CAPTCHA was not correct.

(in french) :

• Attaque à base de réutilisation de session de CAPTCHA détectée.
• La réponse saisie pour le CAPTCHA est incorrecte.

EXAMPLE :

For example, with a “TT7Zi” Captcha image, when I submit the form (in anonymous) : I get the following errors on the screen :

• CAPTCHA session reuse attack detected.
• The answer you entered for the CAPTCHA was not correct.

And in the logs (watchdog) I get two times the same entry :

Message xxxxxx_contact_form post blocked by CAPTCHA module: challenge Image (by module image_captcha), user answered “TT7Zi”, but the solution was “542dda8e8d7fda2358b4b2f319ef198b”.

Any solution for this issue will be really helpful. Thank you all.