1408370 - Firefox hijacks Telegram link open handler in Windows Registry

Status: RESOLVED INCOMPLETE

(Firefox :: File Handling, defect)

Description

[Ali Shamakhi]

Attachment: fix-telegram-link-uri-handler.reg

User Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:56.0) Gecko/20100101 Firefox/56.0
Build ID: 20170926190823

Steps to reproduce:

(Having Telegram installed for a while)
Opening any Telegram link in form of "tg://" in Firefox


Actual results:

Firefox opens Telegram by setting its working directory to the Firefox's working directory. This causes Telegram to be opened as not logged in to any account (at the welcome screen).

I've figured out that Firefox is doing this by modifying some Windows Registry values for handling "tg://" links. Those are Default values (@) at keys:

[HKEY_CLASSES_ROOT\tdesktop.tg\shell\open\command]
[HKEY_CLASSES_ROOT\tg\shell\open\command]
[HKEY_CURRENT_USER\Software\Classes\tdesktop.tg\shell\open\command]
[HKEY_CURRENT_USER\Software\Classes\tg\shell\open\command]

Values are the launcher command and parameters for executing Telegram, and the "-workdir" parameter was set to Firefox's install location.



Expected results:

If Firefox was not changing the values, Telegram would open and function normally.
I've installed Telegram (at D:\Telegram Desktop) in another PC with no Firefox, and found that the default values for those registry keys are these (exported registry keys is attached in a reg file):

[HKEY_CLASSES_ROOT\tdesktop.tg\shell\open\command]
"D:\Telegram Desktop\Telegram.exe" -workdir="C:\Windows\system32" -- "%1"

[HKEY_CLASSES_ROOT\tg\shell\open\command]
"D:\Telegram Desktop\Telegram.exe" -workdir="C:\Windows\system32" -- "%1"

[HKEY_CURRENT_USER\Software\Classes\tdesktop.tg\shell\open\command]
"D:\Telegram Desktop\Telegram.exe" -- "%1"

[HKEY_CURRENT_USER\Software\Classes\tg\shell\open\command]
"D:\Telegram Desktop\Telegram.exe" -- "%1"

Comment 1

[:Paolo Amadini]

(In reply to Ali Shamakhi from comment #0)
> I've figured out that Firefox is doing this by modifying some Windows
> Registry values for handling "tg://" links.

I would be surprised if this was done by a plain installation of Firefox. I suspect add-ons or third-party software may be involved.

You may try the following in this order:
1. Install the latest Firefox Beta
2. Start Firefox Beta and close it again, in case some third-party software is monitoring new installations
3. Ensure the registry keys have the correct values
4. Start Firefox Beta again

At this point, I would expect the registry keys to be unmodified. Can you check?