Firefox forces MOVE instead of COPY when dragging text from external apps (Notepad++ → Firefox)

I’ve been experiencing an issue where dragging a URL or text from Notepad++ into Firefox causes the text to be removed from Notepad++. It behaves like Firefox is requesting a MOVE operation instead of a COPY. This only happens with Firefox, dragging the same text into Vivaldi, Chrome, Edge, etc. does not delete the text. Here’s everything I’ve already tried: 1. '''Verified it’s not a Notepad++ setting''' Disabled “Multi‑Editing” in Notepad++ Restarted Notepad++ Confirmed the issue only happens with Firefox, not other browsers 2. '''Tested Firefox Safe/Troubleshoot Mode''' Launched Firefox in Troubleshoot Mode (no extensions, no themes, default settings) The issue still happens there, so it’s not caused by an extension or add‑on 3. '''Created a brand‑new Firefox profile''' Went to about:profiles Created a completely new, clean profile with no imported data Tested dragging again — the issue still happens even in a fresh profile 4. '''Reset and recreated drag‑related Firefox preferences''' I checked and/or reset the following in about:config: ui.dragThresholdX → recreated as Integer = 16 ui.dragThresholdY → recreated as Integer = 16 dom.event.clipboardevents.enabled → set to false browser.drag_out_of_frame_style → set to 0 browser.search.context.loadInBackground → false browser.tabs.searchclipboardfor.middleclick → false browser.urlbar.update1 → false widget.disable-native-drag → true Restarted Firefox after each change. None of these resolved the issue. 5. '''Tested modifier‑key behavior''' Holding CTRL while dragging does prevent the text from being deleted → This confirms Firefox is treating normal drags as MOVE instead of COPY. 6. '''Verified it’s Firefox‑only''' Dragging the same text from Notepad++ into Vivaldi, Chrome, Edge, Word, Notepad, etc. works normally Only Firefox causes the source text to be removed I'm at a loss of what the issue can be or where to go from here or if there is no fix at the moment.