Firefox gives a warning when you open an "executable" file from that downloads list.

Previously, there was a preference called browser.download.manager.alertOnEXEOpen you could set to false to avoid the message. That preference was removed.

But don't panic, there is a new one. Here's how you set it up:

(0) Select and copy the new preference name:

browser.download.skipConfirmLaunchExecutable

(1) In a new tab, type about:config in the address bar and press Enter/Return. Click the button accepting the risk -- this change involves some risk.

(2) In the search box above the list, type or paste EXE and pause while the list is filtered

(3) Right-click a blank space and click New, then Boolean.

• In the little dialog that comes up, paste the preference name and click OK.

• Click true and then click OK. (If you do not get the options of true and false, you might not have selected Boolean, so cancel and start again.)

Now when you launch a .jnlp or other executable from the Downloads list, it should go straight to the system without the intervening confirmation dialog. Not the safest thing if you tend to download questionable files, but more convenient.

(4) To switch this off, to protect against accidentally running other kinds of executables, double-click the browser.download.skipConfirmLaunchExecutable preference to switch the value from true to false (then in the future, when this is needed, double-click to switch it to true)

Sorry, I answered a different JNLP-related question than the one you asked!

Since JNLP is considered an executable file, there's no "Open" option for it, no. Did that just change in Firefox 67?

There should be an Open choice available for JNLP (Java Network Launched Application; application/x-java-jnlp-file) when Java is installed properly (I still have it on Linux).

Maybe check the handlers.json file in the profile folder (see about:profiles -> root). Do the .jnlp file start JavaWS when you download and save the file?

You can also check the Network Monitor what MIME that the server ends for this .jnlp file.

• https://developer.mozilla.org/en-US/Tools/Network_Monitor

cor-el said

There should be an Open choice available for JNLP (Java Network Launched Application; application/x-java-jnlp-file) when Java is installed properly (I still have it on Linux).

Yup, it is a Windows thing:

• "On Windows, the `sExecutableExts` list is used to determine whether files count as executable. For executable files, we will not offer an "open with" option when downloading, only "save as"." https://dxr.mozilla.org/mozilla-release/source/toolkit/components/reputationservice/ApplicationReputation.cpp#111

• Executable extensions list includes .jnlp: https://dxr.mozilla.org/mozilla-release/source/xpcom/io/nsLocalFileCommon.cpp#25

jscher2000 said

• "On Windows, the `sExecutableExts` list is used to determine whether files count as executable. For executable files, we will not offer an "open with" option when downloading, only "save as"." https://dxr.mozilla.org/mozilla-release/source/toolkit/components/reputationservice/ApplicationReputation.cpp#111

• Executable extensions list includes .jnlp: https://dxr.mozilla.org/mozilla-release/source/xpcom/io/nsLocalFileCommon.cpp#25

Thank you guys for your help. Really appreciate it.

Do I understand this correctly: when an extension is in the executable extensions list Firefox will not display a "open with" option, right?

In this case there has to be an issue in Firefox v.66 because I can prove that a .jnlp file can be "opened with Java Web Start" on FF v.66. I have a testsystem with version 66.0.4 installed where I can demonstrate this. As soon as I update Firefox to version 67 the option disappears.

There have been security changes in Firefox 67 regarding how to handle executable files. This was discussed in a restricted bug (1392955), we can only see the outcome.

• https://www.mozilla.org/en-US/security/advisories/mfsa2019-13/#CVE-2019-11696

Thank you. This is exactly what I needed to know.