how do I know if my MacBook was jailbroken?

What is the app and where did you get the app from? If you got it anywhere than directly from the publisher, I would suspect the app was tampered with.

Also, "jailbreaking" is a term attributed iDevices when bypassing certain functions so that one can install non-App Store apps on the iDevices which is a meaningless term for a Mac since you can install apps directly from any vendor. This also makes me suspect of the app.

sayednaser Said:

"how do I know if my MacBook was jailbroken? I opened my bank software/app on my MacBook Air and it told me that my Mac had been jailbroke"

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Scan your Mac for Malware: 

Use MalwareBytes for Mac --- This is software that searches for malware/adware. So, scan with it and then remove what is found. Once removed, uninstall MalwareBytes for Mac. Then restart the Mac.

Downloads:

1. Malwarebytes Anti-Malware for Mac
2. Malwarebytes Uninstaller

sayednaser Said:

"how do I know if my MacBook was jailbroken?: free from malware and problem not solved"

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Contact Apple Support:

If something is jailbroken, then contact Apple Support. If need her, perform a screensharing session with them, showing them this message upfront.

Apple Contact Info:

• Contact Us - Choose Locations
• Proceed from there, as necessary
• Why the Wait: Phone calls are taking a bit to go through at the moment, due to lots of calls. With the Coronavirus Pandemic, many are at home at the moment, with much time on their hands to contact Apple. So, just stay on the line, and you will get through.