Use wp_rand() instead of mt_rand() for CAPTCHA file name generation to make it harder for attackers to predict its next value

The CAPTCHA system made use of the internal PHP random function mt_rand() when determining which CAPTCHA to phrases to present. With this new improvement, the CAPTCHA system instead makes use of the WordPress-specific wp_rand() function, which utilizes different randomization algorithms, making the CAPTCHA system much harder to predict.

This vulnerability affects the following application versions:

• Contact Form 7 3.6
• Contact Form 7 3.7
• Contact Form 7 3.7.1
• Contact Form 7 3.7.2
• Contact Form 7 3.8
• Contact Form 7 3.8.1
• Contact Form 7 3.9
• Contact Form 7 3.9.1
• Contact Form 7 3.9.2
• Contact Form 7 3.9.3
• Contact Form 7 3.9-beta
• Contact Form 7 4.0
• Contact Form 7 4.0.1
• Contact Form 7 4.0.2
• Contact Form 7 4.0.3
• Contact Form 7 4.1
• Contact Form 7 4.1-beta