Facebook tests prompts that ask users if they're worried a friend is "becoming an extremist"

"We are partnering with NGOs and academic experts in this space and hope to have more to share in the future," Stone added.

One of the alerts, a screen grab of which made the rounds on social media Thursday, asks users, "Are you concerned that someone you know is becoming an extremist?"

"We care about preventing extremism on Facebook," explained that alert, according to a screen grab posted on social media. "Others in your situation have received confidential support."

The alert then redirects the user to a support page.

"Violent groups try to manipulate your anger and disappointment," another alert reads. "You can take action now to protect yourself and others."