Turn off Firefox add-on updates.

Firefox checks for new versions of your installed add-ons once per day, and at other designated times, such as when upgrading to a new version of Firefox. By default, Firefox will check the Mozilla Add-ons Gallery for updates, but individual add-on developers may set their add-ons to check their own websites for updates if they are not hosted with Mozilla.

Each of these checks contains the same information that every web request does: your IP address, browser version, operating system, locale, etc. Mozilla uses this information in aggregate for statistics and usage information.

GENERAL REQUEST DATA OF FIREFOX ADDON UPDATE [informational only]

GET /update/VersionCheck.php?reqVersion=2&id=yslow@yahoo-inc.com&version=3.1.8.1-signed.1-signed&maxAppVersion=56.*&status=userDisabled&appID={ec8030f7-c20a-464f-9b0e-13a3a9e97384}&appVersion=69.0.1&appOS=Darwin&appABI=x86_64-gcc3&locale=en-US&currentAppVersion=69.0.1&updateType=112&compatMode=normal HTTP/1.1
Host: versioncheck-bg.addons.mozilla.org
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.14; rv:69.0) Gecko/20100101 Firefox/69.0
Accept: */*
Accept-Language: en-US,en;q=0.5
Accept-Encoding: gzip, deflate
Connection: close
Pragma: no-cache
Cache-Control: no-cache

To turn add-on updates off entirely, follow these instructions:

1. In Firefox’s location bar, type about:config
2. A warning may be displayed if this is your first time modifying Firefox config. If you wish to continue, click the button.
3. In the Filter text box, type extensions.update.enabled
4. Double click the extensions.update.enabled item to turn it from true to false
5. in the Filter text box, again look for services.sync.prefs.sync.extensions.update.enabled
6. Turn it from true to false

Firefox will no longer check your add-ons for updates.