Recently, I was using Special:MultipleUpload to upload many images at once. However, one image just wouldn't upload - it gave an error message "File extension ".png" does not match the detected MIME type of the file (image/webp)."
The image was a png image, so I don't know why it wasn't uploading. I deleted the image, downloaded it from the source again, and uploaded it, but it still wouldn't work. I tried this multiple times, but it still didn't work. I then messaged another user asking if he was able to upload it. He successfully uploaded it without any issues.
Does anyone know what the problem might be? This only happened with one image out of all twenty I was trying to upload.