• Using a separate Firefox profile:
  • Profile Manager http://kb.mozillazine.org/Profile_Manager
  • Profilist plugin: https://addons.mozilla.org/en-US/firefox/addon/profilist/
• Security features to disable:
  • disable CSP: http://stackoverflow.com/questions/27323631/how-to-override-content-security-policy-while-including-script-in-browser-js-con
  • xframe options: https://stackoverflow.com/questions/12881789/disable-x-frame-option-on-client-side

See addon:

• https://addons.mozilla.org/en-US/firefox/addon/ignore-x-frame-options-header/. Make sure to use https://addons.mozilla.org/en-US/firefox/addon/crxviewer/ to check that the source code of the extension matches https://github.com/ThomazPom/Moz-Ext-Ignore-X-Frame-Options/blob/3aca6f43e808604475a4abea5a5c28c87ce6c807/background.js. Once installed, disable automatic updates.