Start Firefox in Safe Mode to check if one of the extensions ("3-bar" menu button or Tools -> Add-ons -> Extensions) or if hardware acceleration or userChrome.css is causing the problem.

• switch to the DEFAULT theme: "3-bar" menu button or Tools -> Add-ons -> Themes
• do NOT click the "Refresh Firefox" button on the Safe Mode start window

• https://support.mozilla.org/en-US/kb/troubleshoot-firefox-issues-using-safe-mode
• https://support.mozilla.org/en-US/kb/troubleshoot-extensions-themes-to-fix-problems

Your proposals didn't help to solve the problem. Several FF users have the same problem as me – people with other setting/preferences in FF.

I've contacted a person who doesn't work with FF, but where FF is installed with the default settings - NO add-ons - NO userChrome.css ect., and the problem with double 'pasting' in Gmail manifests there also.

Yes, there have been several reports and it seems it is a gmail issue.

See also:

• Bug 1699935 - Clipboard image copy-pastes twice in Gmail

(please do not comment in bug reports
https://bugzilla.mozilla.org/page.cgi?id=etiquette.html)

Its not just gmail. For last 3 years I loaded CTRL-V a document into a university peer discussion board. I could paste an image. NOW I cant. It isnt the university tech; other students still can. It says in the error message when I use CTRL -V that "Browser does not support pasteing from clipboard.". That is the problem. I want to keep using firefox. But if I have to stop and uninstall you and USE GOOGLE, then I will. Im a customer. Help me. Thanks