Firefox users who allow the browser to install and run studies -- functionality that seeds random users with new features before release to the broader user base -- may have found themselves with an unwelcome add-on installed over the weekend called Looking Glass.

First noticed by a number of Reddit users, Looking Glass was an alternate reality game tie-in for Mr Robot that inverted certain text.

"The Mr Robot series centers around the theme of online privacy and security," a Mozilla support note said. "One of the 10 guiding principles of Mozilla's mission is that individuals' security and privacy on the internet are fundamental and must not be treated as optional."

To interpret: In order to educate users about privacy, it must be impinged with functionality the user didn't ask for. Such Orwellian logic.

Now before we go over the top with "War is peace. Freedom is slavery. Ignorance is strength", never attribute to malice that which is adequately explained by stupidity, and right on cue is the marketing head at Mozilla.

"Our goal with the custom experience we created with Mr Robot was to engage our users in a fun and unique way," CMO Jascha Kaykas-Wolff told Gizmodo.

Kaykas-Wolff went on to say the add-on would be moved to the Add-On store, and that it never collected any data and had to be explicitly enabled to work. However, that explanation misses the point that the whole furore began when someone looked in their add-on listing, not when text was transformed.

The Looking Glass snafu arrives in the wake of the well-received Quantum release that has recorded over 170 million installs as of last Wednesday.

Earlier this year, Mozilla found itself in hot water over its decision to use a plug-in called Cliqz that recommended links to news, weather, sport, and other websites directly in the search bar based on a user's history and activities to a tiny number of users in Germany.

"Users who receive a version of Firefox with Cliqz will have their browsing activity sent to Cliqz servers, including the URLs of pages they visit," Mozilla said at the time. "Cliqz uses several techniques to attempt to remove sensitive information from this browsing data before it is sent from Firefox.

"Cliqz does not build browsing profiles for individual users, and discards the user's IP address once the data is collected."

At the start of the year, Mozilla acquired Pocket, and after integrating it tightly into Firefox years prior.

To get rid of Pocket, Firefox users should head to about:config and set the extensions.pocket.enabled preference to false.

To remove your browser from Firefox studies, user needs to go to about:preferences#privacy and uncheck the relevant checkbox.

Once completed, Firefox is back to being a good browser, albeit one that needs constant vigilance to prevent the next great idea from Mozilla HQ from adding functionality you don't want.

Updated 21:34 pm AEDT 18 December 2017: Clarified Pocket integration and acquisition timeline.

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