Overview
Malicious code could be injected into the app, potentially stealing data or redirecting users to harmful sites. Cross-site scripting (XSS) is a type of injection attack where malicious scripts are injected into web pages or apps. In mobile apps, XSS can occur in WebViews (components that render web content), or other areas where user input is reflected in the UI without proper sanitization. There are three main types of XSS: stored (persistent), reflected (non-persistent), and DOM-based. These vulnerabilities can allow attackers to execute malicious scripts in the context of a trusted user session, potentially leading to theft of session cookies, credentials, or other sensitive information.
Risk factors
Cross-site scripting attacks can arise from these conditions:
- Failure in properly sanitizing or encoding input data before displaying it in WebViews or app interfaces.
- Use of WebViews without proper security configurations, such as enabling JavaScript unnecessarily or not using safe browsing modes.
- Failure to validate and sanitize inputs in forms, URLs, or user-generated content fields.
- Cookies used for authentication or session management without proper security settings (e.g., HttpOnly, Secure) increase the risk.
Consequences
If a cross-site scripting vulnerability is exploited, the following could happen:
- Session hijacking: Attackers can steal session cookies and impersonate users.
- Credential theft: Malicious scripts can steal user credentials entered in forms.
- Malicious redirection: Users can be redirected to phishing sites or other malicious websites.
- Data theft: Attackers can steal sensitive information by injecting malicious JavaScript into the app’s WebViews.
- Reputation damage: XSS attacks can lead to a loss of trust in the application, especially if users’ data is stolen or sessions are hijacked.
Solutions and best practices
To mitigate the risks and associated with cross-site scripting, organizations should implement the following security measures:
- Input sanitization: Sanitize and validate all user inputs before reflecting them in the user interface or passing them to WebViews.
- Secure WebView configuration: Disable unnecessary JavaScript execution and prevent access to sensitive local resources within WebViews.
- Content security policy (CSP): Implement a strong content security policy to mitigate the risk of XSS in WebViews.
- Cookie security: Use the HttpOnly and Secure flags on cookies to prevent client-side scripts from accessing them.
- App shielding: Application shielding can be employed to prevent tampering with WebView configurations and prevent the injection of malicious scripts.
Further reading