CVE-2025-25300 in smartbanner.js
Summary
by MITRE • 02/18/2025
smartbanner.js is a customizable smart app banner for iOS and Android. Prior to version 1.14.1, clicking on smartbanner `View` link and navigating to 3rd party page leaves `window.opener` exposed. It may allow hostile third parties to abuse `window.opener`, e.g. by redirection or injection on the original page with smartbanner. `rel="noopener"` is automatically populated to links as of `v1.14.1` which is a recommended upgrade to resolve the vulnerability. Some workarounds are available for those who cannot upgrade. Ensure `View` link is only taking users to App Store or Google Play Store where security is guarded by respective app store security teams. If `View` link is going to a third party page, limit smartbanner.js to be used on iOS that decreases the scope of the vulnerability since as of Safari 12.1, `rel="noopener"` is imposed on all `target="_blank"` links. Version 1.14.1 of smartbanner.js contains a fix for the issue.
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Analysis
by VulDB Data Team • 02/18/2025
The vulnerability identified as CVE-2025-25300 affects smartbanner.js, a JavaScript library designed to display customizable app banners for mobile platforms including iOS and Android. This library serves as a user interface component that prompts visitors to download mobile applications by displaying promotional banners that can direct users to app stores or third-party websites. The security flaw specifically manifests in versions prior to 1.14.1 where the implementation fails to properly secure navigation links that open in new browser tabs or windows. When users click on the smartbanner's "View" link to navigate to external pages, the library does not adequately protect against potential security exploits that could arise from the exposed window.opener property.
The technical flaw stems from the improper handling of hyperlink attributes when creating navigation links within the smartbanner component. The window.opener property in web browsers provides a reference to the window that opened the current window, which creates potential security risks when navigating from a trusted origin to an untrusted third-party domain. In this case, when a user clicks on the smartbanner's "View" link and the target page opens in a new tab, the newly opened window maintains a reference back to the original page through window.opener. This creates an attack surface where malicious third-party websites could potentially manipulate the original page through techniques such as window navigation redirection or script injection attacks, as outlined in the CWE-1021 category for improper handling of window.opener.
The operational impact of this vulnerability extends beyond simple user experience concerns to encompass significant security implications for websites implementing the smartbanner.js library. Websites that utilize this library without proper protection could become vectors for cross-site scripting attacks or phishing attempts, particularly when the "View" link directs users to domains outside of the app store ecosystems. The vulnerability affects both iOS and Android platforms, though the risk profile varies based on the browser implementation and platform security measures. Attackers could exploit this weakness to redirect users to malicious sites or inject harmful content into the original page, potentially compromising user data or system integrity. This issue aligns with ATT&CK technique T1531 which covers "Run-time Application Prototyping" and represents a classic example of how seemingly benign UI components can introduce security vulnerabilities through improper implementation of browser security mechanisms.
The recommended solution involves upgrading to smartbanner.js version 1.14.1 or later, which automatically implements the rel="noopener" attribute on all generated links. This attribute prevents the newly opened window from accessing the window.opener property, effectively eliminating the attack vector. The rel="noopener" mechanism is a well-established security pattern that has been recommended by security standards and browser vendors as a mitigation strategy for exactly this type of vulnerability. For organizations unable to immediately upgrade, several workarounds are available including ensuring that View links only direct users to official app stores where security is managed by the respective platform teams. Additionally, limiting the library usage to iOS platforms provides partial mitigation since Safari 12.1 and later versions automatically enforce rel="noopener" on all target="_blank" links, reducing the scope of the vulnerability. These mitigation strategies align with the principle of defense in depth and demonstrate the importance of implementing proper security controls even in seemingly simple web components. The vulnerability serves as a reminder of how third-party libraries can introduce security risks and emphasizes the need for continuous security assessment of all components integrated into web applications.