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This article describes why you can get AUS: Update XML File Malformed (200) when Firefox checks for updates.
Table of Contents
Disable any extensions that may be blocking access to the update server, such as Noscript. For more information, see Troubleshoot extensions, themes and hardware acceleration issues to solve common Firefox problems.
Firefox can't access secure sites
Firefox uses secure sites when it checks for updates. Make sure your Firefox is able to access secure sites without errors or prompts.
- Click the Firefox menu and select .Click the Firefox menu at the top of the screen and select .Click the Firefox menu and select .
- Start Firefox.
- In the Location Bar, type https://addons.mozilla.org and press EnterReturn.
- If you get an error loading the site, see Websites don't load - troubleshoot and fix error messages.
- If you get a prompt for your master password or for a proxy password, then Firefox is not able to check for updates until you receive that prompt and enter the correct password. As a workaround, you can periodically check for updates manually after you've entered your password.
Incorrect update URL setting
Firefox may be set to use an incorrect address when checking for updates.
- Type about:config in the address bar and press EnterReturn.
A warning page may appear. Click to continue to the about:config page.
- Search for the preference app.update.url.
- Right-clickHold down the Ctrl key while you click app.update.url and click .
- If is disabled, Firefox is already set to use the correct update address, so this isn't your problem.
Now that Firefox is configured with the correct address, it may be able to update without error.
Cookies - Incorrectly set or Cannot be set
Firefox may not be able to set or read cookies when it checks for updates. Make sure your Firefox is able set or access cookies, especially when using Stealther and/or other Privacy and Security add-ons.
- Temporarily disable Stealther and/or other Privacy and Security add-ons.
- Click the menu button and select . .
- Select the panel.
- Click the button to open the Cookies window.
- Find a cookie beginning with the name aus2. If it exists, select the site and click
Eset security software
If nothing else works, you can always download the latest version of Firefox from http://www.getfirefox.com and install it over top of your existing version. You won't lose your bookmarks or other settings. To prevent the error dialog from coming up, you can turn off automatic updates.