Added user compatibility check for AJAX requests

The lack of authorization resulted in multiple vulnerabilities such as the ability to send out newsletters with custom content, local file inclusion, deleting and importing subscribers, and more.

This vulnerability affects the following application versions:

• Popup Builder by Forward Looking 3.0.5
• Popup Builder by Forward Looking 3.0.6
• Popup Builder by Forward Looking 3.0.7
• Popup Builder by Forward Looking 3.0.8
• Popup Builder by Forward Looking 3.0.9
• Popup Builder by Forward Looking 3.0.9.1
• Popup Builder by Forward Looking 3.1
• Popup Builder by Forward Looking 3.1.1
• Popup Builder by Forward Looking 3.1.2
• Popup Builder by Forward Looking 3.1.3
• Popup Builder by Forward Looking 3.1.4
• Popup Builder by Forward Looking 3.1.4.1
• Popup Builder by Forward Looking 3.1.5
• Popup Builder by Forward Looking 3.1.5.1
• Popup Builder by Forward Looking 3.1.5.2
• Popup Builder by Forward Looking 3.1.6
• Popup Builder by Forward Looking 3.1.6.1
• Popup Builder by Forward Looking 3.1.7
• Popup Builder by Forward Looking 3.1.7.1
• Popup Builder by Forward Looking 3.1.8
• Popup Builder by Forward Looking 3.1.9
• Popup Builder by Forward Looking 3.2
• Popup Builder by Forward Looking 3.3
• Popup Builder by Forward Looking 3.4
• Popup Builder by Forward Looking 3.7
• Popup Builder by Forward Looking 3.7.1
• Popup Builder by Forward Looking 3.41
• Popup Builder by Forward Looking 3.42
• Popup Builder by Forward Looking 3.43
• Popup Builder by Forward Looking 3.44
• Popup Builder by Forward Looking 3.45
• Popup Builder by Forward Looking 3.46
• Popup Builder by Forward Looking 3.47
• Popup Builder by Forward Looking 3.48
• Popup Builder by Forward Looking 3.49
• Popup Builder by Forward Looking 3.50
• Popup Builder by Forward Looking 3.51
• Popup Builder by Forward Looking 3.52
• Popup Builder by Forward Looking 3.53
• Popup Builder by Forward Looking 3.54
• Popup Builder by Forward Looking 3.55
• Popup Builder by Forward Looking 3.56
• Popup Builder by Forward Looking 3.57
• Popup Builder by Forward Looking 3.58
• Popup Builder by Forward Looking 3.59
• Popup Builder by Forward Looking 3.60
• Popup Builder by Forward Looking 3.61
• Popup Builder by Forward Looking 3.61.1
• Popup Builder by Forward Looking 3.62
• Popup Builder by Forward Looking 3.62.1
• Popup Builder by Forward Looking 3.63
• Popup Builder by Forward Looking 3.64
• Popup Builder by Forward Looking 3.64.1
• Popup Builder by Forward Looking 3.65
• Popup Builder by Forward Looking 3.65.1
• Popup Builder by Forward Looking 3.65.2
• Popup Builder by Forward Looking 3.66
• Popup Builder by Forward Looking 3.67
• Popup Builder by Forward Looking 3.68.1
• Popup Builder by Forward Looking 3.68.2
• Popup Builder by Forward Looking 3.68.3
• Popup Builder by Forward Looking 3.68.4
• Popup Builder by Forward Looking 3.68.5
• Popup Builder by Forward Looking 3.68.5.1
• Popup Builder by Forward Looking 3.68.5.2
• Popup Builder by Forward Looking 3.69
• Popup Builder by Forward Looking 3.69.1
• Popup Builder by Forward Looking 3.69.2
• Popup Builder by Forward Looking 3.69.3
• Popup Builder by Forward Looking 3.69.4
• Popup Builder by Forward Looking 3.69.5
• Popup Builder by Forward Looking 3.69.6
• Popup Builder by Forward Looking 3.71
• Popup Builder by Forward Looking 3.72