Transformation of downloaded .dmg files to .exe files (#2)

Continuing coverage of a mysterious change in filename extension to .exe for downloaded items

We continue to report on a perplexing issue where certain .dmg files downloaded from the Web transform into files with .exe extensions either temporarily (during the download) or permanently. There's likely a good explanation for this probably innocuous issue, but we've yet to discover it.

Only temporary for most users For the majority of those experiencing this issue, the switch to a .exe extension happens only temporarily, while the file is downloading. Once the disk image (.dmg) is finished downloading, it appears with the proper extension and can be normally mounted. If, however, the download is interrupted, the .exe extension can remain.

As described by one reader:

"I experience randomly created .exe files on download frequently. They appear to be temp files and *almost* always disappear as soon as the download completes."

Still a .dmg, even with the .exe extension In most cases, the .exe file resultant from this issue is in fact a working .dmg file, which can be double-clicked and mounted normally despite its improper extension.

In cases where double-clicking the .exe file does not result in a normal mount, simply changing the extension from .exe to .dmg can result in proper function.

Only happens with Firefox Most of the reports we've received on this issue so far have been from users of Firefox. Attempting the same downloads in Safari results in a proper .dmg extension from the get-go.

One reader writes:

"I am using the G5 Optimized Firefox browser and also get .exe files whenever I try to download a DMG type file. Im usually switch to Safari and download the file successfully."

Possible fixes

Download to a different folder Oddly, some users have reported that this issue manifests with certain folders and not others. If, for instance, you are experiencing this issue when downloading files to the Desktop, try crating a new folder called "Downloads" on the Desktop and see if the issue manifests there as well.

MacFixIt reader Scott writes:

"I usually have a "Downloads" folder on my desktop where Firefox and Safari puts its downloads. For whatever reason, I put that folder in my Documents folder and put an alias of the folder (also called "Downloads") on the desktop. I didn't change the preset location for downloads in Firefox.

"Then, when I attempted a Firefox download, it failed, and I got an error message saying something like it couldn't find "xxxxxxx.exe" where the name of the file was very much like the one in MacFixit today ("kv92ngz5.exe"). At that point, I put my Downloads back on the desktop and relaunched Firefox and reset the download location to that folder again. Downloads worked again."

Reset Launch Services In the event that this issue has something to do with corruption of the Launch Services database -- used to associate documents with applications -- you can reset it via one of these methods:

The easiest is to use a utility like LSRefresh. Several general-purpose Mac OS X maintenance utilities, including AppleJack, can perform this function as well.

You can also manually delete the Mac OS X Launch Services caches from the directory: /Library/Caches/. Delete any files that are named as such:

  • com.apple.LaunchServices-[...].csstore
  • e.g.: com.apple.LaunchServices-015501.csstore
Also, navigate to ~/Library/Preferences and delete the file:
  • com.apple.LaunchServices.plist

then restart.

Alternatively, you can use this AppleScript, provided by a member of the MacFixIt forums.

Feedback? Late-breakers@macfixit.com.

Previous coverage:

Resources
  • LSRefresh
  • AppleJack
  • AppleScript
  • Late-breakers@macfixit.com
  • Mysterious appearance of ....
  • More from Late-Breakers
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