Show the issue. It works for me. see screenshot What version of Firefox? What version of windows? What security software are you running? Did you try Firefox in Troubleshoot Mode?

When I try to attach a file message says "Attachment failed" at attachment bar, also get a pop up error message. See screenshot.

What version of Firefox? ---- V 130.0 What version of windows? ---- Windows 10 What security software are you running? ---- McAfee Did you try Firefox in Troubleshoot Mode? ----- Yes and attachments work OK

I believe this started after I installed the latest Firefox update.

Attachments work OK in Microsoft Edge,

Did you try Firefox in Troubleshoot Mode? ----- Yes and attachments work OK

Here is the answer to your issue. You need to see which add-on is causing your issue.