: The Joint Photographic Experts Group file format , which is the most universally recognized extension for compressed digital images.

Rename the file to use the correct three-letter extension: change image.jpg to image.png if it's a PNG. Remove any special characters (e.g., & , $ , or spaces) and replace them with underscores or hyphens to avoid confusing the upload script.

What or content management system (CMS) is throwing this error?

To understand what a query like this targets, it helps to dissect it into separate technical elements: