Mozilla Firefox update error: Update XML file malformed (200)

KB Solution ID: SOLN2371|Last Revised: December 09, 2009

The Update XML file malformed (200) error message may occur after an attempt to update Mozilla Firefox. The error message may vary slightly depending on which version of Mozilla Firefox is installed. You must exclude the * certificate so SSL protocol checking functionality will not interfere with the update process.


  1. Open ESET Smart Security. How do I open my ESET product?

  2. Press the F5 button on your keyboard to open the Advanced Setup window.

  3. Navigate to Antivirus and antispyware Protocol filtering SSL in the advanced settings of your ESET product and click the Ask about non-visited sites (exclusions can be set) radiobutton. Click OK to confirm.

  4. Open Mozilla Firefox and in the Help menu select the Check for updates... option.

  5. A pop-up window will display informing you about the Firefox application trying to communicate via SSL. Click Exclude.

  6. This excludes the Mozilla Firefox certificate from being checked by your ESET product. To verify this setting navigate to Antivirus and antispyware Protocol filtering SSL Certificates Excluded certificates.

  7. After confirming the exclusion, navigate to Antivirus and Antispyware Protocol filtering SSL and revert the SSL filtering mode settings, i.e. select the option Always scan SSL protocol. Verify the option Apply created exceptions based on certificates is selected.

  8. Mozilla Firefox will be able to complete the update without interference after you finalize these changes.

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