The Bug:

Pistons placed adjacent to the edge spawn protection can be activated.

Steps to Reproduce:

• Start a server and join it.
• Give operator permissions to yourself.
• Set the world spawn to your current location.
• Locate the edge of spawn protection.
• Place a piston adjacent to the edge of spawn protection.
• Place a lever next to the piston.
• Remove your operator permissions.
• Give operator permissions to any person other than yourself.
• Attempt to activate the piston by using the lever you previously placed.
  →  Notice how you are able to activate the piston, which can lead to blocks being moved in spawn protection.