Bottom line: 2018 has been the worst year in Facebook's history, as the social network lurches from one PR disaster to another, so it's surprising to learn the company is testing an Instagram setting that many will see as a violation of their privacy.

While Facebook's reputation has been tarnished following the fake news, hacking, and privacy controversies, Instagram, which is owned by the social network, has mostly come out unscathed. But that may change after the photo- and video-sharing app was found to be testing a privacy setting that would allow it to share users' locations with Facebook.

The revelation comes after Instagram co-founders Kevin Systrom and Mike Krieger resigned from their respective roles as chief executive and chief technical officer last week. The pair were reportedly frustrated with "an uptick in day-to-day involvement from [Facebook CEO Mark] Zuckerberg, who has become more reliant on Instagram in planning for Facebook's future."

The prototype Instagram system could allow Facebook to "periodically add your current precise location to your Location History even if you leave the [instagram] app," according the setting's 'Learn more' button. The data would help Facebook target users with more relevant ads and content.

The setting was discovered by Jane Manchun Wong, who in the past has revealed other features being tested by Facebook, Instagram, and Twitter ahead of time. One element that will likely please users is that the feature was defaulted to off in the prototype; hopefully, it will remain an opt-in option if and when a final version rolls out. It appears that the setting could also arrive in the Messenger app, too.

In a statement given to TechCrunch, a Facebook spokesperson said: "To confirm, we haven't introduced updates to our location settings. As you know, we often work on ideas that may evolve over time or ultimately not be tested or released. Instagram does not currently store Location History; we'll keep people updated with any changes to our location settings in the future."