When you export an image in Photoshop, e.g. quick export of a .PNG, it overwrites existing images without warning if you omit the extension. So if IMG01.PNG exists and you're saving a completely different IMG01 with the extension mask set to *.PNG, the 'file exists' check fails and the old file is overwritten without warning. If you enter IMG01.PNG as filename, the 'file exists' check succeeds and you get the expected warning. It's a simple bug. If the extension is missing from the filename, the code should add it and then check. It's a small change but it saves you from unwanted file overwrites. This bug has been here for years. Please fix it.