Escaping HTML tags in the protect module to avoid XSS

The protect module was vulnerable to XSS.

This vulnerability affects the following application versions:

• Jetpack 3.4
• Jetpack 3.4.1
• Jetpack 3.4.2
• Jetpack 3.4.3
• Jetpack 3.4.4
• Jetpack 3.4.5
• Jetpack 3.4.6
• Jetpack 3.5
• Jetpack 3.5.1
• Jetpack 3.5.2
• Jetpack 3.5.3
• Jetpack 3.5.4
• Jetpack 3.5.5
• Jetpack 3.5.6