MIT provides essentially none in my opinion. App Inventor 2 is freely made available for educational and experimental use. It is not designed as a secure compiler for commercial apps. App Inventor 2 provides an obfuscation Block that provides minimal hacking protection; third parties provide means to encrypt your data that could provide additional security but only if you yourself code the safe guards if the data is stored on MIT's servers (i.e. CloudDB using default settings)..
Privacy Policy and Terms of Use explains how you can use MIT App Inventor and what they do to protect your data.
This is probably what you want to know:
Disclaimer of Warranty / Indemnification/Limitation of Liabilities
THE SITE IS PROVIDED "AS IS" AND "AS AVAILABLE" WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESS OR IMPLIED, INCLUDING WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR USE FOR A PARTICULAR PURPOSE, AND NON-INFRINGEMENT. MIT does not warrant the Site will operate in an uninterrupted or error-free manner or that the Site is free of viruses or other harmful components. Use of information obtained from or through this Site is at your own risk. Your access to or download of software, information, materials, or data through the Site or any reference sites is at your own discretion and risk and that you will be solely responsible for any damage to your property (including your computer system) or loss of data that results from the download or use of such material or data.
IN PARTICULAR, MIT WILL HAVE NO LIABILITY FOR ANY CONSEQUENTIAL, INDIRECT, PUNITIVE, SPECIAL, EXEMPLARY OR INCIDENTAL DAMAGES, WHETHER FORESEEABLE OR UNFORESEEABLE, (INCLUDING, BUT NOT LIMITED TO, CLAIMS FOR DEFAMATION, ERRORS, LOSS OF DATA, OR INTERRUPTION IN AVAILABILITY OF DATA).
also you might like to read this related post Soporte y costos (Support and Costs to use MIT App Inventor)
Possibly; no system is hacker proof.