MacOS Finder URL extension overflow bug

Edit: Dec 2020. Apple fixed this bug in Finder late last year. Keeping this article up here for posterity.

Here’s a fun one.

1. Load this page in Firefox, on a Mac.
2. Drag the red square below to your Desktop.
3. Finder will crash and restart.

 

Yes, I have reported this to apple.

This is a file URL overflow bug. Here the URL is converted to a filename, without proper checking of the extension length. If the extension of the file in the hyperlink URL is longer than 255 characters, finder will crash.

1. This issue can also be reproduced in Google chrome.
2. Create a new bookmark.
3. Edit the bookmark to have the following string for both the Name and URL fields:
   file:///a.AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
4. Next, save the bookmark.
5. Drag the bookmark to the desktop.
6. Finder will crash.