Firefox WebDriver (Marionette) Error

NB: This is not a bug report for Katalon.

This morning, my Firefox WebDriver has suddenly decided to fail completely. I have reported the issue to since I don’t know where marionette bugs are meant to be posted. What follows is the content of the report:

I have been using marionette via Katalon ( very
successfully. This morning, suddenly, the webdriver is bombing out (the
browser opens correctly to a blank url and then closes immediately).
The console in Katalon shows the following toward the end of the output
(if you need more log lines, let me know, but these seemed the most

1540907780940    Marionette    DEBUG    Remote service is active
1540907781069    Marionette    DEBUG    Accepted connection 0 from
1540907781072    Marionette    TRACE    0 -> [0,1,"newSession",{"acceptInsecureCerts":true,"browserName":"firefox","capabilities":{"desiredCapabilities":{"acceptInsecureCerts":true,"browserName":"firefox","proxy":{"proxyType":"direct"}}},"proxy":{"proxyType":"direct"}}]
1540907781073    Marionette    TRACE    0 <- [1,1,{"error":"unknown command","message":"newSession","stacktrace":"WebDriverError@chrome://marionette/content/error.js:178: ... et@chrome://marionette/content/server.js:245:8\n_onJSONObjectReady/<@chrome://marionette/content/transport.js:490:9\n"},null]
Oct 30, 2018 8:56:21 AM org.openqa.selenium.remote.ErrorCodes toStatus
INFO: HTTP Status: '404' -> incorrect JSON status mapping for 'unknown error' (500 expected)
10-30-2018 08:56:21 AM - [FAILED] - Unable to open browser with url: '' (Root cause: org.openqa.selenium.WebDriverException: newSession
Build info: version: '3.7.1', revision: '8a0099a', time: '2017-11-06T21:07:36.161Z'
System info: host: 'RUSS-BLAH', ip: '', 'Windows 7', os.arch: 'amd64', os.version: '6.1', java.version: '1.8.0_102'
Driver info: driver.version: CGeckoDriver
remote stacktrace: stack backtrace:
   0:           0x4821c4 - <no info>
   1:           0x482933 - <no info>
   2:           0x445159 - <no info>
   3:           0x44eff6 - <no info>
   4:           0x4322e1 - <no info>
   5:           0x40ba4e - <no info>
   6:           0x4119b9 - <no info>
   7:           0x6d2c89 - <no info>
   8:           0x426006 - <no info>
   9:           0x6cd490 - <no info>
  10:         0x776559cd - BaseThreadInitThunk) 

If any Katalon person knows how to fix this, by all means, please help!

Fix below.


If anyone else is suffering this issue (it’s appeared on three separate machines, here) download the latest geckodriver from here:

Place it in your Katalon drivers folder – on Windows…


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