Really Simple Security pro

• Extensive scan which enables you to detect the source of mixed content that couldn’t be fixed automatically, with fix button
• Premium email support
• HttpOnly and secure flags to make the cookies more secure
• Improve security by enabling HTTP Strict Transport Security for your site
• Submit your site to the HSTS preload list
• Warning by email and in your SSL dashboard when your certificate is about to expire
• Mixed content fixer for the back-end

Note: You have to install and activate its free version in prior to using this plugn. Download it on Wordpress.org here.