What MIME type validation does
From version 4.24.9, the Iptanus File Upload plugin validates the MIME type of every uploaded file.
A MIME type describes the nature and format of a file.
During validation, the MIME type must match the file’s extension. The MIME type of an image with a .png extension, for example, must be image/png.
The plugin keeps a standard list of extension-to-MIME-type mappings. If an uploaded file’s combination is not on that list, the file is treated as suspicious and rejected, and the user sees this message:
Why files that are fine get rejected
MIME type validation is sometimes too strict, and can block files that are perfectly good.
To deal with that, the plugin has a Quarantine feature. With it switched on, the plugin no longer rejects files whose MIME type it cannot verify — it puts them in the quarantine instead.
Accepting a rejected file
To make the plugin accept a file that was rejected on MIME type grounds:
1. Switch on the Quarantine feature in the plugin’s Settings (instructions).
2. Upload the file again. This time the message tells the user the file has been quarantined:
3. Go to the Quarantine tab in the plugin’s Dashboard area and find the file:
4. Press 
to accept the file.
5. On the next screen, tick the box to add an upload exception, so that future uploads with the same extension and MIME type are accepted automatically.
6. Press the Accept and Add Exception button. The file is then stored in its final location.
The exception that prevents a repeat
The exception is added on the Exceptions page, so that new files with the same extension and MIME type are accepted automatically from now on.
Can’t I just turn off this feature, instead of quarantine the files?
There should be an option to turn this feature off completely. Website is breaking and dealing with files as they come is not reasonable
This doesn’t work at all. The quarantine exception bypass doesn’t appear, and even adding MIME types in the exceptions in the advanced settings doesn’t show anything on the exceptions screen. In addition, users still get the error about the rejected file even if it gets uploaded and goes into quarantine. I am concerned about this plugin no longer being developed or supported, as it’s been almost a week since I submitted a support email regarding this issue with no response.