Ultimately the developer is responsible for maintaining a level of security assurance in visualized data. Google Visualizations, and any code that evokes the Google APIs for that matter, must be aware of the potential security risk that the use of an API on a data source creates. Google provides some guidance on this issue in their Terms of Service and Program Policy.
Security and data privacy with charts
Developers are responsible for abiding by the Google Terms of Service and Program Policy when publishing.
For more information please visit https://google-developers.appspot.com/chart/interactive/docs/security_privacy.