What OS? If windows, home or pro and are you running any security software besides MS Defender? What version of Firefox? Show the issue. Provide steps to replicate the issue.

Mac OS 15.4 Firefox version 137.01

As for replicating the issue, that's not likely to happen unless you have Alma.

Here's a screenshot.. but yeah if I go to Editing Actions> Field Information. I get this error.

Is your issue similar to this? https://support.mozilla.org/en-US/questions/1505079#answer-1724770 You should provide steps to replicate your issue. The screenshot you posted leaves me....

No, it has nothing to do with iframe.

I'm trying to open a page within the existing page. And for some reason, Firefox has decided it can't do that anymore because it could be used to hijack the browser and download malicious material. But this is the Library of Congress webpage, it's not malicious at all.

i just need to figure out the security settings that need to change so I can tell Firefox to trust the.. library of congress.

Show the issue.

Here is a screen recording of the issue.

https://drive.google.com/file/d/1-6SmwuMMSSifRQaK90kPZOCSzNLLfy1J/view?usp=sharing

I don't know how to show the issue anymore than this.

I'm pretty sure either the website has disabled embedding, or the website that's being embedded already has another embed in it. I'm not too sure.

To visit a site that displays this error message, you can right-click the embed and select Open Link in New Tab or Open Link in New Window. Alternatively, you can copy and paste the link into an already open new tab or window. However, be aware that the embedding page may not function correctly without access to the blocked content. In such cases, you may need to contact the owner of the problematic site for further assistance.

Sourced from https://support.mozilla.org/en-US/kb/xframe-neterror-page

Yes, I understand what is happening.

I need it to STOP IT from happening so that the site can work as it is supposed to, not telling me to just open in a new window cause that doesn't solve the issue. That's just having another website open.

I understand now. I've done a bit of research, and sadly you can't disable Firefox's enforcement of X-Frame-Options or CSP frame-ancestors (which is what's causing the issue) as they're server-side security policies. No built-in setting exists to turn this off due to clickjacking risks. Sorry.