In every project I open, whenever I view the project in fullscreen, there is a single row of white pixels (relative to the 480x240 stage, not however many pixels are on the user's monitor) below the stage. I have tested this on multiple computers, from Windows 10 desktops to Chromebooks to the Mac I am using right now, and they have all had this blank space.

Note that this only occurs when the project is in fullscreen mode, and does not occur in any other view mode.

Example:

Please ignore the “screenshot” word bubble, as I have the screenshot tool in my dock and it was still highlighted at the time the screenshot was taken.

My browser / operating system: MacOS Macintosh X 10.14.2, Chrome 71.0.3578.98, No Flash version detected

Bump, as this still hasn't been fixed.

Yep!

CR. My browser / operating system: Windows NT 10.0, Chrome 76.0.3809.100, No Flash version detected

Banana

Tested, can confirm I've seen it
My browser / operating system: MacOS Macintosh X 10.13.6, Chrome 76.0.3809.100
Seems like it definitely happens regardless of your operating system or browser

Thanks to the Bugs & Glitches directory I found this, and it was exactly what I was looking for.

CR (can replicate). It's easier to see if you increase the page zoom level.

This probably happens because of the design of the smooth edges around the player.