In this situation, there are several actions you could take to verify if the application is trustworthy. For instance, you could ask about or research the company and people who created the app and what their background and credibility are like. If the team behind it is full of credible, knowledgeable employees, it would suggest that it is more trustworthy. In particular, if the application was created by a well-known, reputable financial company, it would suggest it was trustworthy because those sorts of companies would have too much to lose to release an application that was not secure.
In terms of functionality and security, you might also ask about how the application runs to keep your data safe. For example, you might ask how the application verifies a user’s identity. Some financial applications use strategies like passwords, Touch ID, and Face ID to ensure that the person using the application is a person who is allowed to access the accounts. Understanding what this application uses to vet its users would help you get a sense of how secure it is.