Mozilla, which makes the popular Firefox web browser, has become the first major organisation to stop advertising on Facebook amid the controversy over the Cambridge Analytica files.

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The non-profit organisation says it is “pressing pause” on Facebook advertising, at least until the social network strengthens its protections of user data.

Denelle Dixon, Mozilla’s chief business and legal officer, said it had investigated Facebook’s data controls as a result of the Observer’s reporting that 50 million profiles were improperly transferred to the political consultancy firm Cambridge Analyitica.

“We found that its current default settings leave access open to a lot of data,” she said, “particularly with respect to settings for third party apps.

“We are encouraged that Mark Zuckerberg has promised to improve the privacy settings and make them more protective. When Facebook takes stronger action in how it shares customer data, specifically strengthening its default privacy settings for third party apps, we’ll consider returning.

“We look forward to Facebook instituting some of the things that Zuckerberg promised,” Dixon added.

Before Zuckerberg broke his silence on Wednesday night and discussed the changes Facebook would make in response to the scandal, Mozilla had proposed its own fixes.

The organisation suggested a blanket ban on third parties accessing information about the friends of people who use an app, noting that “the internet is transformative because it’s a place to explore, transact, connect, and create. Trust is key to that.

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“We’re pushing Facebook to improve its privacy practices not just because of its 2 billion users, but also for the health of the internet broadly.”

Other advertisers have threatened to respond similarly. The British advertiser umbrella group Isba will meet with Facebook executives this week, the Times has reported, to make clear that its members do not find it acceptable that user data has made it off site.

The paper also reported several investors who have proposed moving Facebook shares out of their “ethical” funds, including the nordic bank Nordea and the German group Union Investment.

But some are optimistic about Facebook’s ability to weather the storm. Debra Aho Williamson, the principal analyst at eMarketer, said: “This specific incident is not likely to cause advertisers to leave Facebook, but it will cause them to think twice about how data about Facebook’s users is handled.

“Facebook’s advertising system depends on user data, and it has used that data to develop targeted advertising capabilities that are better than any other company can offer. If Facebook were forced to change the way it uses data or the way its ad products work, then advertisers may become less enamored with it.

“But for now, we see no signs of advertiser demand diminishing; on the contrary, worldwide ad spending on Facebook is expected to rise more than 22% this year, reaching $48.85bn [£35.5bn]. Its share of the global digital ad market will rise to nearly 18%.”

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