This post is mirrored from my old blog.
This was a fun one. The challenge site provided a file upload control, which allowed us to upload images to the site. Upon uploading an image, the image would be displayed under a new file name, along with the associated Image Description, GPS Longitude and GPS Latitude tags.
My first thought was to insert some PHP into the exif data, so I downloaded the very useful ExifTool to attempt this.
This attempt failed, so I pulled out the next trick in the bag. I threw an apostrophe into the Image Description tag and uploaded the file. Internal Server Error! SQL injection? I think so!
With some tinkering, I managed to successfully exploit the SQLi to get the flag.