Like the title says.
Wondering if it is possible to implement such a feature. The tooltip notification could be something very small with a fast timeout just saying “Firefox pasted from your clipboard” or “Firefox accessed from your clipboard” (could also appear when copying something).
Similar to how current Android and iOS does it.
We could also get a widget in the taskbar that could show the clipboard access history, showing which apps accessed it recently. This widget could also list access history for mic, camera, and location, but that is another brainstorm idea for the future.
This feature and widget could prove very useful in detecting if any application is suspiciously accessing your clipboard contents by itself.
This is surely a bigger problem on X than on Wayland, since on X every app can see every clipboard item and history you ever copied, any time it wants. On Wayland, to my knowledge, it seems to me that only the currently focused app can read your clipboard, but that is still very unsafe.
We seriously need to start considering safety and privacy on very little things like this, all around KDE.