Nonfree (proprietary) software is very often malware (designed to mistreat the user). Nonfree software is controlled by its developers, which puts them in a position of power over the users; that is the basic injustice. The developers often exercise that power to the detriment of the users they ought to serve.
Here are examples of proprietary software that has something worse than a back door.
The developer of Ham Radio Deluxe sabotaged a customer's installation as punishment for posting a negative review.
Most proprietary software companies don't use their power so harshly, but the point is that they all have such power.
HP's firmware downgrade imposed DRM on some printers, which now refuse to function with third-party ink cartridges.
Once Microsoft has tricked a user into accepting installation of Windows 10, they find that they are denied the option to cancel or even postpone the imposed date of installation.
This demonstrates what we've said for years: using proprietary software means letting someone have power over you, and you're going to get screwed sooner or later.
The Apple Music client program scans the user's file system for music files, copies them to an Apple server, and deletes them.
Apple stops users from fixing the security bugs in Quicktime for Windows, while refusing to fix them itself.
iOS version 9 for iThings sabotages them irreparably if they were repaired by someone other than Apple. Apple eventually backed off from this policy under criticism from the users. However, it has not acknowledged that this was wrong.
Phillips “smart” lightbulbs had initially been designed to interact with other companies' smart light bulbs, but later the company updated the firmware to disallow interoperability.
If a product is “smart”, and you didn't build it, it is cleverly serving its manufacturer against you.
Microsoft is forcibly pushing Windows update to its version 10, ignoring the flag on Windows 7 or 8 that you could set to not upgrade. This reaffirms the presence of a universal back door in Windows 7 and 8.
Windows 10 “upgrades” delete applications without asking permission.
Google has long had a back door to remotely unlock an Android device, unless its disk is encrypted (possible since Android 5.0 Lollipop, but still not quite the default).
Users report Microsoft is forcing them to replace Windows 7 and 8 with all-spying Windows 10.
This seems to involve use of a back door in Windows 7 and 8.
Lenovo stealthily installed crapware and spyware via BIOS on Windows installs. Note that the specific sabotage method Lenovo used did not affect GNU/Linux; also, a “clean” Windows install is not really clean since Microsoft puts in its own malware.
Vizio used a firmware “upgrade” to make its TVs snoop on what users watch. The TVs did not do that when first sold.
Amazon downgraded the software in users' Swindles so that those already rooted would cease to function at all.
Apple deleted from iPods the music that users had got from internet music stores that competed with iTunes.
Microsoft informs the NSA of bugs in Windows before fixing them.
We can be quite sure this EULA is is unjust because injustice is the only motive for imposing an EULA.
FTDI's proprietary driver for its USB-to-serial chips has been designed to sabotage alternative compatible chips so that they no longer work. Microsoft is installing this automatically as an “upgrade”.
Microsoft cut off security fixes for Windows XP, except to some big users that pay exorbitantly.
Microsoft is going to cut off support for some Internet Explorer versions in the same way.
A person or company has the right to cease to work on a particular program; the wrong here is Microsoft does this after having made the users dependent on Microsoft, because they are not free to ask anyone else to work on the program for them.
The NSA has put back doors into nonfree encryption software. We don't know which ones they are, but we can be sure they include some widely used systems. This reinforces the point that you can never trust the security of nonfree software.
An Apple firmware “upgrade” bricked iPhones that had been unlocked. The “upgrade” also deactivated applications not approved by Apple censorship. All this was apparently intentional.
Some proprietary games lure children to spend their parents' money.
Adobe applications have time bombs: they stop working after a certain time, after which the user must pay to extend the time.
Once there was a problem with the servers that these programs use to check who has paid, and the applications refused to work for anyone.
Sony sabotaged the Playstation 3 with a firmware downgrade that removed the feature that allowed users to run GNU/Linux on it.
Sony subsequently sent police after Geohot, after he cracked the code that blocked users from changing the firmware, and we responded by calling for a boycott of Sony .
In a court settlement Sony is now paying for the sabotage.
LG disabled network features on previously purchased “smart” TVs, unless the purchasers agreed to let LG begin to snoop on them and distribute their personal data.
Oracle's nonfree Java plug-in for browsers sneakily installs other annoying proprietary software.
That article disregards all other bad things about proprietary software. For instance, it regards the inclusion of proprietary Flash Player (which has a surveillance feature and DRM) in Chrome as a good thing. Chrome is a proprietary browser with a universal back door.
We don't agree with the article's views on those issues, but we present it as a factual reference.