Unable to edit HTML in SSPR e-mail templates

When editing an e-mail template, all fields are editable except the HTML Body options. 

In SSPR Configuration Editor, Settings ⇨ Email ⇨ Email Templates, it is not possible to edit any of the HTML fields.  

Fixed with SSPR 4.1.0.3 or later.   

Remove the value in the 'Settings ⇨ Security ⇨ Web Security ⇨ HTTP Content Security Policy Header', save config and then edit.  Be sure to add the value back after editing the email.

Edit the field inside the SSPRConfiguration.xml file.