I've got the same issue, the mouse is going beyond the bottom of the screen and the right of the screen. Very annoying an pretty unplayable.

Same problem here, the cursor moves past the right and bottom boundaries of the screen, is very annoying. I tried various video configurations and the problem remains.

The bug is only in the first mission.

With default settings the mouse is not showing at all. Not in the menus or in the game.

Nope, it's everywhere , including main menu.

okay. When i load a game the bug is back... but when i switch to windows and then back to the game its okay.

Yeah, alt-tab really fixes this issue, thanks for temporary solution

Just noticed GOG added "Warcraft II - Mouse cursor problem" on the Warcraft support page, under known solutions to game issues. Their solution is "Please limit the game's resolution to 640x480, and presentation mode to fullscreen, or Fullscreen - Keep Aspect Ratio, depending on your preferences. Alternatively we highly recommend trying to use Arrow Keys for scrolling."

Still hope this gets patched, but at least Alt+Tabbing does work.

Thanks, that workaround works!!!

Besides this issue, the mouse also moves very awkward. I think there's some major mouse acceleration going on. Really feels terrible. Anyone else seeing this problem?

This is only happening in the enhanced GOG version.

Yeah, I have the same issue. Mouse feels really hard to use. As you wrote, there is some acceleration going on so that small moves are OK, but large mouse moves make the cursor go crazy... And this happens only in the enhanced version.

Same problem on down and right. Tested a lot of settings. And like other it only aper in the enchanted editon not classic.

Try set the mouse to 125hz 400 or 800dpi when playing the game. it did solve the huge mouse isue on speed in Diablo and in this game for me. I have MarkC_Windows_10+8.x+7_MouseFix installed dont rly know if it do effekt it. Did install it for Dablo when trying to fix the problem and dosbox. Changing the report rate, can be a solution.
The mouse running out of screen is not related from what i can se on my few tests.

getting the same issue. it's just like what happened with Diablo before they patched it out

Edit: Alt + Tabbing a few times seems to fix the mouse issue, as other people have mentioned