Security questions for mobile app vendors
Non-technical procurement teams can effectively assess the security of mobile app vendors by asking targeted questions. This helps build trust and ensure data integrity without requiring technical expertise.
- Require compliance with the OWASP MASVS standard in the contract to make security requirements concrete.
- Ask for concrete evidence of secure data storage, such as the use of iOS Keychain and Android Keystore.
- Verify how communication between the app and backend (API) is secured, for example through TLS with certificate pinning.
- Make clear agreements about regular security updates and maintenance responsibilities after launch.
- Ask for a recent, anonymized penetration test report as evidence of external security validation.
Security expectations in outsourced mobile app development
Security remains vague when a vendor offers only general reassurance and there is no fixed standard underlying the agreement. In outsourced mobile app development, a useful expectation therefore starts not with isolated promises, but with a testable foundation for what counts as security. In this context, OWASP MASVS serves that role: it makes security requirements contractually concrete, so discussions about authentication, authorization, API security, and data handling do not get stuck in general wording.
Without such a shared foundation, room for interpretation quickly arises between client and vendor. One party may assume security is part of the agreed delivery, while the other sees it as additional scope or a later refinement. OWASP MASVS creates boundaries by making security requirements definable in advance. For many mobile apps, Level 1 is the minimum standard. That does not automatically answer every project detail, but it does prevent the lower boundary from remaining unspoken during proposal, contract, and delivery.
Security ownership belongs in the same discussion, because a standard alone does not assign responsibility. In outsourcing, it must be clear who is responsible for translating security requirements into the delivered product, and who remains involved after the app goes live. Post-launch updates make that distinction especially visible: if maintenance and security updates are not explicitly assigned, it remains unclear who follows up on new security requirements or changes after launch. Security then shifts from an agreed delivery component to an open-ended issue.
For non-technical teams, the core issue is therefore not assessing code themselves, but being able to trace claims back to a standard and to ownership. A vendor that accepts OWASP MASVS as a contractual foundation and provides clarity on security ownership and post-launch updates makes the security expectation verifiable. If that link is missing, it remains unclear even after selection whether the minimum security baseline was actually agreed and who remains responsible once the app is in use.
Risks of missed checks during vendor selection
Security responsibilities that are not defined after go-live leave a direct gap in the maintenance of a mobile app. It then remains unclear who handles security updates, who follows up on deviations, and who is liable if personal data is exposed due to avoidable technical errors. That shifts a selection discussion from verifiable agreements to assumptions, while the operational consequences only become visible once the app is already in use.
A second risk arises when a vendor is assessed based on general reassurance rather than verifiable security controls. In that situation, there is no technical validation on the buyer’s side, a broad claim such as security-by-design carries too much weight, and what is actually included in the mobile app remains hidden. The chain of error is concrete: lack of validation leads to reliance on general claims, hardcoded API keys can then remain in the mobile code, and unauthorized access to backend systems becomes possible. For a non-technical team, this is exactly the difficult point: the presentation looks convincing, but the actual control is missing.
That lack of clear boundaries also affects trust in the vendor during the shortlist phase. As long as security ownership is not explicitly tied to data storage, API security, and long-term maintenance, it remains unclear whether security is part of the delivery or will return later as an open issue. As a result, proposals and discussions become difficult to compare. One party sells trust with general language, while another may work more concretely without that difference becoming visible if the checks are not defined in advance.
For apps that process personal data, this does not remain an abstract risk but becomes a governance and financial issue. If an avoidable technical error leads to a breach, it can result in legal liability and fines under the GDPR. That is precisely why vague vendor selection continues to have consequences after delivery: unclear post-launch updates at the front end in unclear ownership, delayed maintenance, and liability in the event of a data breach at the back end.
Essential security aspects to verify
Security claims remain vague when a mobile app vendor does not make clear how access is protected and how data is secured in transit. In the shortlist phase, verification is therefore not about reading source code, but about verifiable security aspects and a recognizable basis for assessment. OWASP MASVS provides a useful reference point for mobile app security requirements, while NIST SP 800-163 helps structure that assessment. For non-technical teams, that makes the difference between general reassurance and a vendor that can explain its approach along testable lines.
Authentication and authorization should be on the table as separate checkpoints. A vendor can only speak credibly about security if it becomes clear how access to the app is established and how permissions are then limited. That distinction prevents “being logged in” from being confused with “being allowed to access everything.” For a procurement or operations team, this is mainly a verification question: can the vendor explain in plain language which security layer determines who gets in and which layer determines what is accessible afterward? If that distinction is missing in discussions or proposals, it remains unclear whether access control has really been thought through or is only being presented as a general feature.
API security requires equally direct verification, because the mobile app and the underlying systems exchange data through that connection. The relevant check here is not a technical detail in isolation, but whether the vendor can demonstrate that this communication is secured through TLS with certificate pinning for critical mobile transactions. In practice, the risk arises the moment an app sends data to a backend and that protective layer is not explicitly part of the security approach. A core part of the mobile chain then remains dependent on trust rather than demonstrable protection, even though that is exactly where sensitive exchanges take place.
Data handling should be explicitly verified for the same reason. ENISA places mobile app security firmly in the context of data protection, which makes the handling of data more than a technical side issue. A vendor should therefore not only say that data is secure, but also show that data protection is part of how the app is assessed and scoped. Combined with OWASP MASVS and NIST SP 800-163, this creates a practical minimum baseline for vendor selection: authentication, authorization, API security, and data handling must be named separately and be verifiable. As soon as one of these elements remains implicit, the assessment shifts from verifiable security aspects to unsupported assumptions about the mobile app vendor.
Checklist of security questions for mobile app vendors
Security claims remain vague when a vendor does not mention a testable standard, causing shortlist discussions to quickly get stuck in reassuring wording without a hard basis for comparison. Use this checklist as a fixed set of security questions for mobile app vendors, with emphasis on OWASP MASVS, secure storage, and evidence from recent penetration tests.
- Ask which level of OWASP MASVS is used as the standard for the project. This question reveals whether the vendor approaches security as a contractual requirement rather than a loose promise. A concrete answer refers to OWASP MASVS as the basis for the mobile app’s security requirements. If the answer remains general, the fixed benchmark by which scope, assessment, and delivery can later be tested is often missing.
- Ask whether OWASP MASVS is explicitly included in the proposal, scope, or contract. This makes it clear whether security is defined in advance or only becomes a topic of discussion later. As soon as this foundation is not explicitly named, room arises for differing interpretations during execution. For non-technical teams, this is a useful control question because they do not need to assess code to see whether the vendor works with a recognizable standard.
- Ask how sensitive data is stored within the app. A credible answer refers to platform-specific secure storage mechanisms such as iOS Keychain and Android Keystore. That shows the vendor is not relying on general language about data handling, but can explain which storage mechanisms are used for sensitive data. If this is not clearly stated, it remains unclear whether sensitive information is being protected appropriately.
- Ask how API keys and user tokens are secured within the app code. This question ties into the same control around secure storage. The vendor does not need to provide deep technical detail here, but should clearly explain that sensitive information is not handled loosely and falls under the same security discipline as other sensitive data in the app. A vague answer without reference to concrete storage mechanisms makes comparison between vendors difficult.
- Ask for a recent, anonymized penetration test report from a comparable mobile project. This is a direct piece of evidence that goes beyond a presentation or general security text in a proposal. A vendor that can show such a report demonstrates that security has also been tested externally or formally. If this example is completely absent, the assessment remains based mainly on explanation rather than demonstrable control.
- Ask how the vendor documents these three points together. The combination of a fixed standard such as OWASP MASVS, a concrete explanation of secure storage through iOS Keychain or Android Keystore, and a recent penetration test report provides a much more useful basis for comparison than isolated reassurances. As soon as one of these elements is missing, it becomes harder to compare security claims across mobile app vendors consistently.
Common mistakes when skipping security checks
Hardcoded API keys in mobile code often remain invisible during vendor selection when security checks are replaced by general reassurance. As a result, the assessment shifts from verifiable security to trust in sales language, while the actual flaw only becomes visible after the app has already been connected to backend systems.
- A common mistake is relying on broad claims such as security-by-design without technical validation of what that actually means. In that situation, a vendor may include API keys hardcoded in the mobile code. The chain is then direct: the key is in the app, the app communicates with backend systems, and unauthorized access comes within reach. For a non-technical team, this is exactly the kind of risk that remains hidden during the proposal and selection phase, because the explanation can sound convincing while the underlying control is missing.
- The damage from such a missed check is not limited to a technical flaw. As soon as personal data is exposed through that route due to an avoidable technical error, the issue shifts to legal liability and possible fines under the GDPR. That makes vendor choice not only a matter of trust, but also of governance and financial exposure.
- A second mistake arises after go-live: security ownership for post-launch updates is not defined. Then there is no clear maintenance responsibility when new OS vulnerabilities appear. The app continues to run on modern devices, but without patches the situation shifts from functional to insecure. That loss of clear ownership affects day-to-day operations, because no one can clearly point to who is responsible for fixing new security issues.
- That lack of clarity has two concrete consequences. Externally, end-user trust declines as soon as the app no longer feels secure on modern devices. Internally, recovery costs rise because fundamental security flaws have to be corrected afterward that could already have been identified during development or vendor selection. The combination of delayed maintenance and after-the-fact remediation then ends not in a minor incident, but in an insecure app on modern devices.
Synthesis of security expectations and responsibilities
Security remains hard to grasp when no one is explicitly responsible for agreements around updates, vulnerabilities, and personal data. Security ownership then shifts from proposal to execution without fixed boundaries, while the risk still remains directly with the client if avoidable technical errors lead to the exposure of personal data. In that situation, a reassuring explanation from the vendor is not the same as demonstrable responsibility, because the operational and legal consequences do not stay with the presentation but with the live app and the data it processes.
That tension only really becomes visible after go-live. A mobile app does not change only during the development phase; software updates and vulnerability management remain part of the security expectation afterward as well. If post-launch maintenance remains implicit, room arises for delay, discussion about ownership, and uncertainty about who handles software updates. This is not an administrative detail. It is precisely here that it becomes visible whether a vendor uses a transparent patch management process, or whether security in practice becomes dependent on loose commitments and ad hoc follow-up.
For non-technical teams, the core issue is therefore less about assessing technical depth and more about distinguishing clear responsibility from noncommittal wording. Security ownership only gains meaning when the phase after delivery is also clearly defined: who manages vulnerabilities, who processes updates, and who bears the consequences if that happens too late or incompletely. As soon as that line is missing, the risk quietly shifts from vendor to client, with possible legal liability and fines under the GDPR in the event of a personal data breach caused by avoidable technical errors.
