When she asked Siri "What's my name?" and "Who do I call most?", Apple's digital assistant promptly pulled up the device owner's recent calls.
What's more, even though the iPhone was password protected, @afronomics_ was able to find out the owner's first and last name, where she lives and even where her car is parked - all from the device's notifications panel.
Fortunately, the person was able to locate her lost iPhone and recover it from the Twitter user.
Unsurprisingly, she was shocked to learn that @afronomics_ was able to access a sizable amount of personal information about her, even when the device was locked.
Since the security flaw was identified, Apple has announced that it's aware of the issue and that it will be fixed in an upcoming software update.
"We are aware of the issue and it will be addressed in an upcoming software update," Apple said.
Apple released its latest mobile operating system, iOS 11.3, late last month, but it's unclear if the bug was patched when the update was shipped.
However, there are a few temporary fixes that can resolve the issue in the meantime.
For apps with sensitive data, navigate to Settings, then select Notifications and scroll down until you find the app. From there, deselect "Show on Lock Screen."
This will prevent your phone from displaying any notifications from this app on the lock screen.
Additionally, users can disable Siri whenever their phone is locked by going to Settings, selecting Siri & Search and then disabling "Allow Siri When Locked."
Users can also head to Settings, then Touch ID & Passcode and toggle off the "Today View" and "Notifications View" options.
This will prevent Siri from showing information like your calendar, recent contacts and other information from the lock screen.
The concerning security flaw didn't just affect call logs, but also private messages sent via third-party apps, like Facebook Messenger, Slack or Signal.
It's particularly concerning that this affects Signal notifications, as the app is primarily favored for its encrypted messaging features that provide extra security.
Fortunately, any messages or notifications sent to Apple's own Messages app, iMessage, are still protected.
If you ask Siri to read text notifications, she'll tell you to unlock your phone.
Apple started hiding notification previews by default when it rolled out iOS 11 last year.
But the feature has been around for a while, previously allowing users to manually change their settings to hide notification previews.
Now, if you want to read notifications, you have to unlock the phone using Face ID, a password, or some other form of authentication.
Otherwise, you can still turn the feature on by going to Settings and then Notifications.
Under the "When Unlocked" setting, you can choose from "Always" and "Never".
However, choosing "Never" doesn't seem to fix the Siri security flaw, according to Gizmodo.