This is a simple user script that brings up an extra confirmation dialog when you click "Approve" in the Suggested Edit review queue. It was written in response to this request for such a feature.
This script is released into the public domain per the Creative Commons CC0 public domain dedication. Feel free to do whatever you want with it.
Download / Install
This user script is hosted on GitHub. If you have a suitable user script management extension (such as GreaseMonkey for Firefox or Tampermonkey for Chrome) installed, clicking the "download / install" button below should bring up a dialog asking you if you want to install this user script:
For more information on how to install user scripts, see the script tag wiki.
This user script has been tested on Mozilla Firefox 27 with GreaseMonkey. It should work on any browser with a compatible user script API, including Google Chrome, Opera and Safari.
The script tries to inject the confirmation dialog handler every time a new review task is loaded, but for some (currently unknown) reason, this doesn't always work. As a safety measure, it also checks twice a second to see if a new task has been loaded, and, if so, adds the handler.
Should both of these methods fail for some reason, the "Approve" button will be shown with red text and border to warn you that clicking it will approve the edit without confirmation. Moving the mouse over the button should trigger a second safety measure that will inject the handler and remove the warning color.