Where are the files you try to paste store (your home directory or elsewhere) ? Are you possibly using the Snap Firefox version as that version has restrictions about accessing files ?

You can try Firefox from the official Mozilla server if you currently use a version from the repositories of your Linux distribution to see if it behaves differently.

• https://www.mozilla.org/en-US/firefox/all/#product-desktop-release

Also make sure you have updated the WhatsApp web app as it may take opening a new WhatsApp web window to get the update notification. WhatsApp put out an update on Monday to fix the paste issue.

I have tried simple things and compare with other browsers problem is coming from Firefox. This action is used every time in the day everyday and it should be corrected! I have seen a lot of forum talking about that and no real solution for years now...

I reinstall Firefox with snap and terminal and now it works for the copy paste and it is twice the speed but now firefox do not start from menu only with command line : killall firefox firefox

I found myself the procedure :

1) remove all old firefox versions : sudo apt purge firefox* sudo apt autoremove --purge dpkg -l | grep '^rc' | awk '{print $2}' | sudo xargs dpkg --purge dpkg -l | grep '^rc' | awk '{print $2}' | xargs sudo apt-get purge

2) install snap and firefox with snap (other repository versions and Software Manager integrzted version are bullshit with 21.2 (Victoria) : copy/ paste error) (used firefox version 29 August 2023 version 117.0 (64-bit)) sudo apt install snapd sudo snap install firefox

Hope this will help others