As an 'extension' to earlier questions on this topic (for instance [here](https://security.stackexchange.com/questions/8550/why-do-chrome-extensions-need-access-to-all-my-data-and-browsing-activity) and [here](https://security.stackexchange.com/questions/15259/worst-case-scenario-what-can-a-chrome-extension-do-with-your-data-on-all-websi)),

 - What makes Firefox extensions (appear) more secure than Chrome extensions?
 - Do they just *appear* to be more secure, or are they really?

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See also:

 - https://security.stackexchange.com/questions/8550/why-do-chrome-extensions-need-access-to-all-my-data-and-browsing-activity
 - https://security.stackexchange.com/questions/15259/worst-case-scenario-what-can-a-chrome-extension-do-with-your-data-on-all-websi
 - https://security.stackexchange.com/questions/38033/are-official-browser-add-ons-really-safe
 - http://lifehacker.com/5990769/why-do-chrome-extensions-need-to-access-all-my-data
 - https://support.google.com/chrome_webstore/answer/186213?hl=en-GB
 - **https://support.mozilla.org/en-US/kb/tips-assessing-safety-extension**
 - **https://support.mozilla.org/en-US/kb/permission-request-messages-firefox-extensions**