Apple has warned iPhone, iPad, and iPod users of a serious security flaw that could allow attackers to take complete control of devices. To fix the vulnerability, they’re urging all users to update their devices ASAP.

Apple sounded the alarm bell on Wednesday August 17, explaining that hackers were actively exploiting the security flaw to attack devices.

They noted that the flaw could allow an application “to execute arbitrary code with kernel privileges,” which effectively gives a would-be attacker full control of the device and its data.

The security breach can "effectively give attackers full access to devices," Rachel Tobac, hacker and CEO of SocialProof Security, said on Twitter.

“For most folks: update software by end of day. If threat model is elevated (journalist, activist, targeted by nation states, etc): update now,” she added.

It’s unclear which devices contained the weak spot, but the latest update is now available for iPhone 6s and later, iPad Pro (all models), iPad Air 2 and later, iPad 5th generation and later, iPad mini 4 and later, and iPod touch (7th generation).