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Discussion Starter · #1 · (Edited)
This tutorial is intended for advanced users only, some technical knowledge and understanding is required.

If you don't know how to use Linux shells, this thread is not for you. Beginner questions, e.g. how to establish a SSH connection or how to handle shells, please ask in other, more suitable forums - such questions are off topic and will be deleted in this thread.

If you have a problem with your TV, you should always contact LG's support first and make use of your warranty options.

Firmware downgrades should be considered as the last possible option for severe problems that are not fixed by LG.

Don't use this option to just play around with the TV's firmware.
This method should work on all reasonably current LG TVs with webOS.

Warnings:
  • Firmware downgrades are not officially supported by LG. If you downgrade the firmware of your LG TV, you will lose the warranty in case of problems. I.e. if problems occur during the downgrade, you are on your own, cannot expect any support from LG and in the worst case have an expensive paperweight.

  • The complete firmware history is stored on the TVs and can neither be deleted by a user factory reset nor by the IN-STOP command. LG can always track when which version of the firmware was on the TV in case of service and thus naturally also detect downgrades.

  • Older firmware versions can sometimes contain critical security vulnerabilities. Not too long ago, almost all models up to (including) those from 2020 were affected by such a vulnerability. Anyone who installs a vulnerable version on their TV should be aware of the considerable danger this poses.

  • Downgrading will of course lose all functionalities and bug fixes that were added by later updates from LG.
    LG unfortunately hardly ever lists details in the official firmware release notes, so it is not always immediately obvious with which version a feature was added or a bug was fixed.

  • There are websites that use the technical possibilities described here to downgrade the firmware of your LG TV.
    I can only strongly advise against opening any of these websites on an LG TV, they may contain bugs and malware.

Instructions:

If you already are a member of the LG Developer site, directly go to step 2.
If you have already set up your SSH access to your TV, go to step 3.

1. Become a member of the LG Developer site
Follow the instructions on this website.


2. Setting up developer access to the TV
Follow the instructions on this website.

First install the webOS TV SDK for the webOS TV CLI on your computer as described in the prerequisites.
You then need to perform the steps "Installing Developer Mode App", "Turning Developer Mode On" and "Connecting with CLI". You do not need to perform the other steps described on the website.

At the end, you should have the webOS Developer App installed on your TV and be logged in with your LG Developer account.


3. Prepare a USB storage device with the desired firmware version
  1. Create a folder with the name LG_DTV in the root folder of your USB storage device.
    The device may use NTFS or FAT32, other file systems are not supported.
  2. Copy the desired firmware file with the epk file extension into the LG_DTV folder, there must be no other firmware file in the folder.
    The file has to be a USB firmware version, not a NSU version.
  3. Make sure that there are no other USB storage devices connected to the TV.

4. Establish a SSH connection to the TV
The RSA key for the connection is located in your SSH user directory, the passphrase for the key is displayed in the Developer Mode app.
Bash:
ssh -p 9922 -i ~/.ssh/tv_webos [email protected] bash -i
5. Start the Software Update App
Launch the software update program on the TV with the following command from the shell opened via the established SSH connection
Bash:
luna-send-pub -d -n 1 -f "luna://com.webos.applicationManager/launch" '{ "id": "com.webos.app.softwareupdate", "params": { "mode": "user", "flagUpdate": true } }'
If successful, the app will open and you will see something like the following screen.

Font Rectangle Technology Darkness Brand



6. Start the Update Process
Press the Update button and wait until the update is complete.
Restart the TV when prompted to do so.


One last note: there is no guarantee that this method will still work in the future. I even assume that LG will block this method at some point.
 

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Thanks for this tutorial. This invoked me to try to start the Software Update app (without parameters) from my ColorControl-app.
It does start up but is immediately closed (because no newer firmware found). Then I appended the "params" part to the payload and lo and behold, the app stays open and the "UPDATE" button is active (similar to your screenshot). When the "flagUpdate" is set to true the version check is probably overruled.
I could incorporate this in a new release of my app, but downgrading will then be a little bit too easy for everyone, so maybe it's better to discuss that first.
I probably want to try it myself too, because I really want to see if I can fix the broken VRR in HDMI 2.1 mode of my C9. Biggest issue is now finding a 04.80.xx version online, because the LG website via the Wayback Machine gives me an access denied error when trying to download those. I could only download 05.00.30.
Does anyone know where to find a 04.80.xx version? I'm wondering if I try such a version first and then a newer version if that would fix the VRR issues of my unit.
 

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Discussion Starter · #4 ·
I could incorporate this in a new release of my app, but downgrading will then be a little bit too easy for everyone, so maybe it's better to discuss that first.
I understand and share the concerns. Otherwise, I probably would have published this information much earlier. But as described in the other thread, the info became public through a Russian forum anyway - and a few people have posted infos about it in several threads here too. Moreover, using the downgrade method via a (possibly shady) website carries even more risks than the downgrade itself already does.

From a technical point of view it should be no problem to integrate this function into your tool.
I'm also a bit conflicted about whether firmware downgrades should be made so easy for everyone. We have already seen that the possibility of installing engineering firmwares are handled a bit too carelessly. Despite all the warnings. Why should it be different in this case?

If you do decide to include the feature in your tool, I would strongly recommend that you only enable it with appropriate warnings and confirmations so that everyone is aware of the risks involved and the loss of warranty.

I may also add some info in the second post in this thread about what a firmware downgrade for your TV means. I'm sure it's not clear to a lot of people.
In very simplified terms, it is roughly comparable to a Windows (or any other OS) downgrade, where all drivers and firmwares of the monitor, GPU, WLAN module, sound card, etc. are downgraded at the same time. And this would all be done without restoring from a backup of the old system.

Biggest issue is now finding a 04.80.xx version online, because the LG website via the Wayback Machine gives me an access denied error when trying to download those.
As already described here, LG removes older firmware versions from their servers. Understandably, since there is no support for these versions and they do not want to distribute buggy versions / versions with security vulnerabilities.
That means you won't get these versions from an official source.
 

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I've managed to downgrade the firmware of my tv while starting the Software Update-app via my tool, so it's definitely working.
And following your considerations I've created a new release of my app which should enable people to downgrade while not visiting obscure websites.
Of course it will display a warning yes/no dialog before activating it and you still have to manually create a preset to launch the Software Update-app.
 

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Hi OP, thanks for the post and information, it looks helpful. It would probably be good to include reasons why you would want to downgrade, e.g. Because dolby vision is broken etc. In fact I'm still hoping they will do one more release that will fix dv so I'm not going to downgrade without a good reason. Perhaps you can expand there? Thank you.
 

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Discussion Starter · #7 ·
It would probably be good to include reasons why you would want to downgrade, e.g. Because dolby vision is broken etc.
Imho I described that pretty clearly in bold red letters: for normal users the only good reason are severe issues that won't get fixed or for which it is unknown if there ever will be a fix.
If something is really broken due to an update, you should primarily contact LG's support and wait for an update. LG usually fixes known problems of this kind within a few weeks.

In fact I'm still hoping they will do one more release that will fix dv so I'm not going to downgrade without a good reason.
What problem from which LG model related to DV are you talking about? The DV issues of the 2019 models should have been fixed with the v05.10.25 update.
But that's a topic for another thread, if you're still having problems with a 2019 model and DV I'd suggest addressing that in the related thread.
 

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All I had to do to downgrade my C8 was:

  • copy an older USB version (not "nsu") of a firmware onto an USB stick the usual way (into "LG_DTV" subdirectory)
  • plug into the TV
  • enter Russian Website
    URL into the WebOS web browser
Is this more complex method applicable to a wider range of sets or supposed to be a better way to do it for some reason?
 

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Discussion Starter · #9 ·
Is this more complex method applicable to a wider range of sets or supposed to be a better way to do it for some reason?
The described method should work on almost all webOS-based LG TVs, including the 2021 models.

As described in the first post:
There are websites that use the technical possibilities described here to downgrade the firmware of your LG TV.
I can only strongly advise against opening any of these websites on an LG TV, they may contain bugs and malware.
You are really playing with fire if you use the mentioned website from a dubious Russian source.

Especially those who have not secured their TV against the latest critical security vulnerabilities. The website (like any other malicious site) could take complete control of the TV, in such a case you would not even notice anything strange.
I'm not saying the site currently does, but it could be misused for other purposes at any time and most users are unlikely to notice until it's too late. It's a matter of trust and there's little reason to trust this website.
 

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The described method should work on almost all webOS-based LG TVs, including the 2021 models.

As described in the first post:

You are really playing with fire if you use the mentioned website from a dubious Russian source.

Especially those who have not secured their TV against the latest critical security vulnerabilities. The website (like any other malicious site) could take complete control of the TV, in such a case you would not even notice anything strange.
I'm not saying the site currently does, but it could be misused for other purposes at any time and most users are unlikely to notice until it's too late. It's a matter of trust and there's little reason to trust this website.
Gottcha, I understand now. (y)
 

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The described method should work on almost all webOS-based LG TVs, including the 2021 models.

As described in the first post:

You are really playing with fire if you use the mentioned website from a dubious Russian source.

Especially those who have not secured their TV against the latest critical security vulnerabilities. The website (like any other malicious site) could take complete control of the TV, in such a case you would not even notice anything strange.
I'm not saying the site currently does, but it could be misused for other purposes at any time and most users are unlikely to notice until it's too late. It's a matter of trust and there's little reason to trust this website.
Is there's an alternative to the Russian site?
 

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Discussion Starter · #12 ·
Is there's an alternative to the Russian site?
Steps 1 to 6 as described in the first post ;)
(For webOS developers, it's just one step.)

There will never be an official trusted website that offers this feature.

Otherwise, @Vinz80 has already suggested a discussion in his first post here, whether he should include the function in his open source tool "ColorControl".
Trust is, of course, also an issue with such a tool. But unlike a website, the source code of a binary executable can't just change from one moment to the next.
 

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2. Setting up developer access to the TV
Follow the instructions on this website.
You need to perform the steps "Installing Developer Mode App", "Turning Developer Mode On" and "Connecting with CLI". You do not need to perform the other steps described on the website.

At the end, you should have the webOS Developer App installed on your TV and be logged in with your LG Developer account.
Quick question re: the Connecting with CLI portion. The instructions themselves imply that the webOS TV CLI app has been installed already on your linux/mac/windows computer. I'm assuming that is necessary to follow through with the rest of the instructions? I'm guessing that's how the key file is made/obtained.
 

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Discussion Starter · #14 · (Edited)
The instructions themselves imply that the webOS TV CLI app has been installed already on your linux/mac/windows computer. I'm assuming that is necessary to follow through with the rest of the instructions? I'm guessing that's how the key file is made/obtained.
Correct. As described on the linked guide from LG:
To use the Developer Mode app, the following should be ready in advance:
  • webOS TV connected with a network
  • PC connected with a network and installed with the webOS TV SDK
  • LG Developer site account
I.e. you need to install the webOS TV SDK before you begin, the SDK contains the webOS TV CLI which is then used in the "Connecting with CLI" section.
I'll add that to the first post to make it clearer.

As soon as you have the private key, you don't need the webOS SDK / webOS TV CLI anymore. From then on, you can do everything necessary via SSH or the Developer Mode app on the TV.
I.e. you only need the webOS TV CLI for the initial connection to the TV.
 

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Ich habe es geschafft, die Firmware meines Fernsehers herunterzustufen, während ich die Software Update-App über mein Tool gestartet habe, also funktioniert es definitiv.
Und nach Ihren Überlegungen habe ich eine neue Version meiner App erstellt, die es Benutzern ermöglichen soll, ein Downgrade durchzuführen, ohne obskure Websites zu besuchen.
Natürlich wird vor der Aktivierung ein Ja/Nein-Warndialog angezeigt und Sie müssen noch manuell eine Voreinstellung erstellen, um die Software Update-App zu starten.
[/ZITIEREN]

Hallo
Wäre es möglich eine kurze Anleitung zu geben wie SIE das geschafft haben?
Ich habe ihre neue Software geladen und gestartet.Ich weiss nicht wie weiter. Bitte geben Sie eine Anleitung
Danke
 
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