This was working flawlessly, solving my issue, until the May 3 update, at which point it stopped working. I removed the plug-in and replaced it with the prior version, and all's well. on Firefox 68.6.1esr (64-bit) Mac OS: Mojave 10.14.6
tried adding to github issues page but having login problem. Essentially +1 to issue titled "Error loading some iframe" I'm fine with prior revision, all is truly well with my use case.
I'm realy sorry about that. This last update solve some important issues, and i'd like to help you Can you open an issue there describing as much as you want the issue /your needs ? https://github.com/ThomazPom/Moz-Ext-Ignore-X-Frame-Options/issues
The extension seems to work on the default whitelist settings. Unfortunately, these default settings are fully permissive for all sites, and when I go to restrict to certain IP addresses and ports or hostnames, iframes stop loading again inside of the parent page. Absolutely nothing I try seems to fix this.