HEIC image attachments uploaded via iPhone improperly get a .jpg extension

[mikewilburn]

Background

iPhones have a setting which permit camera photos from being saved either in high efficiency format (HEIC) or as a JPEG.

(Note: HEIC is the file format name Apple has chosen for the HEIF standard)

If an HEIC image is chosen to be uploaded as an attachment, the app is falsely assigning it a .jpg extension.

Implications

This permits the otherwise unsupported attachment file type to be uploaded under the guise of a JPEG image, which can cause issues when these attachments are opened either on Windows or in a web browser. Windows, Chrome, and Safari have all proved unable to render this image type.

Repro steps

• take a picture with the camera format setting set to HEIC (this setting first emerged on iOS 11, I believe)
• open the data collection app and attach this image to a record in the web map
• save the edits and notice the image has been assigned a .jpg extension
• open the web map in a browser and visit the same record to which this image was attached
• identify the record and attempt to open the image by clicking on it in the list of attachments in the popup that appears
• notice that the image cannot be rendered in the new tab that launches
  • Safari:
  • Chrome:

Note: Using a compatible Windows application that can access these attachments, this is the message that appears when trying to render image attachments: