Beware, KB3135173 for Windows 10 may reset default apps (again)

Martin Brinkmann
Feb 16, 2016
Updated • Jul 5, 2017
Windows, Windows Updates

Reports are coming in that the recent patch for Windows 10 with the identifier KB3135173 may reset default applications on systems it is installed on.

We have talked about Windows 10 resetting default applications before, the first time happening shortly after release of the operating system.

The changes did not affect all users of Windows 10 back then who installed the responsible update at that time but those who were affected reported that default apps for web browsing, pdf viewing and photo viewing were reset, and that programs were removed from the system as well.


KB 3135173 is a cumulative update for Windows 10 that Microsoft released on February 9, 2016. It fixes vulnerabilities reported in the security bulletins MS16-022, MS16-021, MS16-016, MS16-014, MS16-013, MS16-011 and MS16-009.

You find information about these security patches in our patch day overview for February 2016.

Users noticed that something was not right after the patches were installed and the machine rebooted for the first time.

The Action Center started to display one or multiple notifications on the screen that app defaults were reset listing the file type that was reset, and the default system application it was mapped to.

An app default was reset. An app caused a problem with the default setting for .avi files so it was reset to Films & TV.

This happened for custom file associates for file types such as pdf, avi, mp4, jpg or png, and each time the file type was reset to one of the default applications Windows 10 ships with.

Even worse, while it is seemingly possible to associate different apps or programs with the reset file types, Windows 10 would reset those associations a moment later making it impossible to use custom file associations on affected PCs.

Temporary solutions

an app default was reset

So what is the solution for users who are affected by this issue? One course of action is to uninstall the update and block it from running, but it is not suggested since it patches security issues. Removing it will make the system vulnerable to attacks targeting those vulnerabilities.

The Winhelponline Blog created a Registry file that supposedly fixes the issue. I was not able to test it as my test systems were not affected by the issue.

After running the REG fix, open Control Panel > Default Programs and set file associations or default programs as you prefer. None of the built-in Universal Apps should reset the associations from now on. This method has been tested (and works fine) in Windows 10 Build 10586.

Changing file associations on Windows 10

windows 10 default apps

Windows 10 offers several options to choose default applications for file types. The starting point for all of them is the operating system's Settings application.

  1. Tap on Windows-I to open the Settings application.
  2. Navigate to System > Default Apps.

There you find programs or apps associated with popular application types such as email, web browsing or music playing.

You can associate programs with those types right away, but may want to use the three options listed below those for finer controls.

  • Choose default apps by file type displays all known file types and the applications they have been associated with.
  • Choose default apps by protocol displays protocols, such as http or ftp and the applications or programs they are associated with.
  • Set defaults by app finally opens the classic "set default programs" dialog of the Control Panel. Select a program from the list, and associate all file types and protocols with it that it supports (or customize the selection).

set default programs

Closing Words

The resetting of custom file and protocol associations should never happen on its own, and it seems that Microsoft needs to adjust the parameters that are responsible for the resetting to make sure it won't happen again in the future.

For now, it is wise to check default applications, file associations and even installed programs after updates regularly to make sure none were affected by it.

Windows 10 users may also want to create system backups, or at least System Restore points, before running any updates that Microsoft put out for the operating system.

Beware, KB3135173 for Windows 10 may reset default apps (again)
Article Name
Beware, KB3135173 for Windows 10 may reset default apps (again)
The cumulative Windows 10 update KB3135173 may reset default applications and custom file associations after it has been installed.
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  1. Dan Donx said on January 15, 2023 at 10:29 am

    What mental age of reader are you targeting with the first sentence? 10?

    Why not write an article on how to *avoid* upgrading from W10 to W11. Analogous to those like me who avoided upgrading from 7 to 10 for as long as possible.

    If your paymaster Microsoft permits it, of course.

  2. Dexter said on January 15, 2023 at 11:14 am

    5. Rufus
    6. Ventoy

    PS. I hate reading these “SEO optimized” articles.

    1. cdr said on January 15, 2023 at 3:32 pm

      I used Rufus to create an installer for a 6th gen intel i5 that had MBR. It upgraded using Setup. No issues except for Win 11 always prompting me to replace my local account. Still using Win 10 Pro on all my other PCs to avoid the bullying.

  3. sv said on January 15, 2023 at 6:40 pm

    bit pointless to upgrade for the sake of upgrading as you never know when you’ll get locked out because ms might suddenly not provide updates to unsupported systems.

    ps…. time travelling?
    written. Jan 15, 2023
    Updated • Jan 13, 2023

    1. Martin Brinkmann said on January 16, 2023 at 5:49 am

      This happens when you schedule a post in WordPress and update it before setting the publication date.

  4. Anonymous said on January 16, 2023 at 8:24 am

    Anyone willing to downgrade to this awful OS must like inflicting themselves with harm.

  5. basingstoke said on January 16, 2023 at 11:18 am

    I have become convinced now that anybody who has no qualms with using Windows 11/10 must fit into one of the following brackets:

    1) Too young to remember a time before W10 and W11 (doesn’t know better)

    2) Wants to play the latest games on their PC above anything else (or deeply needs some software which already dropped W7 support)

    3) Doesn’t know too much about how computers work, worried that they’d be absolutely lost and in trouble without the “”latest security””

    4) Microsoft apologist that tries to justify that the latest “features” and “changes” are actually a good thing, that improve Windows

    5) Uses their computer to do a bare minimum of like 3 different things, browse web, check emails, etc, so really doesn’t fuss

    Obviously that doesn’t cover everyone, there’s also the category that:

    6) Actually liked W7 more than 10, and held out as long as possible before switching, begrudgingly uses 10 now

    Have I missed any group off this list?

    1. Heinz Strunk said on September 19, 2023 at 3:57 pm

      You have missed in this group just about any professional user that uses business software like CAD programs or ERP Programs which are 99% of all professional users from this list.

      Linux doesn’t help anyone who is not a linux kid and apple is just a fancy facebook machine.

  6. ilev said on August 24, 2023 at 7:34 pm

    Microsoft has removed KB5029351 update

    1. EP said on August 24, 2023 at 9:21 pm

      only from windows update though
      KB5029351 is still available from the ms update catalog site

  7. Anonymous said on August 24, 2023 at 11:05 pm

    1. This update is labaled as PREVIEW if it causes issues to unintelligent people, then they shouldn’t have allowed Preview updates ot install.

    2. I have installed it in a 11 years old computer, and no problems at all.

    3. Making a big drama over a bluescreen for an updated labeled as preview is ridiculous.

    This is probably another BS internet drama where people ran programs and scripts that modified the registry until they broke Windows, just for removing stuff that they weren’t even using just for the sake of it.
    Maybe people should stop playing geeks and actually either use Windows 10 or Windows 11, but don’t try to modify things just for the sake of it.

    Sometimes removing or stopping things (like defender is a perfect example) only need intelligence, not scripts or 3rd party programs that might mess with windows.

  8. john said on August 24, 2023 at 11:17 pm

    Windows 11 was a pointless release, it was just created because some of the Windows team wanted to boost sales with some sort of new and improved Windows 10. Instead, Microsoft cannot support one version well let alone two.

    1. John G. said on August 25, 2023 at 12:08 pm

      Windows 11 is the worst ugly shame by Microsoft ever. They should release with every new W11 version a complete free version of Starallback inside just to make this sh** OS functionally again.

  9. EP said on August 25, 2023 at 3:10 pm

    motherboard maker MSI has recently released a statement regarding the “unsupported processor” blue screen error for their boards using Intel 600/700 series chipsets & to avoid the KB5029351 Win11 update:–UNSUPPORTED-PROCESSOR–Error-Message-of-Windows-11-Update-KB5029351-Preview-142215

  10. EP said on August 29, 2023 at 7:32 pm

    check out the following recent articles:

    Neowin – Microsoft puts little blame on its Windows update after UNSUPPORTED PROCESSOR BSOD bug:

    BleepingComputer – Microsoft blames ‘unsupported processor’ blue screens on OEM vendors:

  11. Leonard Britvolli said on August 30, 2023 at 10:33 pm

    While there may be changes or updates to the Windows 10 Store for Business and Education in the future, it is premature to conclude that it will be discontinued based solely on rumors.

  12. sembrador said on September 5, 2023 at 9:32 pm

    My advice, I left win 15 years ago. Now I’m a happy linux user (linuxmint) but there is Centos, Fedora, Ubuntu depending on your needs.

  13. EP said on September 6, 2023 at 11:55 am

    motherboard maker MSI has recently released new BIOS/firmware updates for their Intel 600 & 700 series motherboards to fix the “UNSUPPORTED_PROCESSOR” problem (Sept. 6):–UNSUPPORTED-PROCESSOR–caused-BSOD-on-MSI-s-Intel-700-and-600-Series-Motherboards-142277

  14. Raphael Benzo said on September 24, 2023 at 9:52 pm

    I try to disable the Diagnostics Tracking Service (Connected Devices Platform User Services) but it wont let me disable it, any help will be greatly appreciated.
    Tank you for your help

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