If you have an iPhone and you see an unknown app installed on your iPhone with the name of Cydia. Then don’t be worry because it’s not harmful to your phone. You can take some awesome advantages of Cydia on your iPhone.
Answer to: What does the Presence of the Cydia app on an IOS Device indicate
The presence of the Cydia app on an IOS Device indicates that the iPhone is jailbroken. Cydia is commonly known as an alternative to AppStore for IOS devices. With the help of Cydia, you can install unauthorized applications on your iPhone and iPad. After jailbreaking a device you can download third-party apps from third party sources.
As we know Apple has strict security rules and it does not let the users install apps from outside of AppStore. Therefore some users install a Jailbreak with tools like Unc0ver Jailbreak and CheckRa1n Jailbreak to get the Cydia app on your device.