iFrame embedding of landing pages?

Is Constant Contact increasing security of their pages? We were embedding an iFrame of a landing page for Newsletter sign up just fine for quite some time, and just recently we discovered that the embed is now being blocked.

We understand the need for security, so...with this change, is there a place where we can provide appropriate domain(s) to allow for x-frame-options and/or a Content Security Policy??? We'd prefer to continue using the embedded content as the widget/inline codse embeds take far too many liberties with injecting conflicting scripts and styles, it is simply not possible for us to use that due to how they are written (it will corrupt our own website's functionality). Sending customers to a completely different domain is also not preferred as our target audience is often not the most technologically savvy.