Escaping multiple html tags of the masterbar to prevent XSS

Masterbar was not properly escaped against an XSS attack.

This vulnerability affects the following application versions:

• Jetpack 4.8
• Jetpack 4.8.1
• Jetpack 4.8.2
• Jetpack 4.8.3
• Jetpack 4.8.4
• Jetpack 4.8.5
• Jetpack 4.9
• Jetpack 4.9.1
• Jetpack 4.9.2
• Jetpack 4.9.3
• Jetpack 4.9-pressable
• Jetpack 5.0
• Jetpack 5.0.1
• Jetpack 5.0.2
• Jetpack 5.0.3