CVE-2021-20728 in Blog App
Summary
by MITRE • 06/09/2021
Improper access control vulnerability in goo blog App for Android ver.1.2.25 and earlier and for iOS ver.1.3.3 and earlier allows a remote attacker to lead a user to access an arbitrary website via the vulnerable App.
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Analysis
by VulDB Data Team • 06/11/2021
This vulnerability represents a critical access control flaw in mobile blogging applications that enables remote attackers to manipulate user navigation through maliciously crafted content. The issue affects both android and ios platforms with specific versions vulnerable including android versions up to 1.2.25 and ios versions up to 1.3.3. The flaw manifests as an improper handling of external URL references within the application's webview or browser component, allowing attackers to inject malicious links that redirect users to arbitrary websites without proper authorization or user consent. This type of vulnerability falls under the CWE-284 access control weakness category, specifically related to inadequate permissions and improper privilege management in mobile application contexts. The attack vector operates through the exploitation of trust relationships within the application's content handling mechanisms, where user interactions with blog posts or comments could inadvertently trigger malicious redirects.
The operational impact of this vulnerability extends beyond simple phishing attacks as it creates a persistent threat vector that can be leveraged for various malicious activities including credential theft, malware distribution, and social engineering campaigns. When users interact with compromised blog content, the application fails to validate or sanitize external links before execution, creating a pathway for attackers to redirect users to malicious domains that may host phishing pages, exploit kits, or other harmful content. This vulnerability particularly affects mobile users who may be less vigilant about URL verification due to the smaller screen sizes and typical mobile browsing behaviors. The threat model aligns with attack techniques documented in the mitre ATT&CK framework under the web application attack patterns, specifically targeting user execution and initial access phases where attackers leverage application trust relationships to compromise user systems.
Security professionals should implement comprehensive mitigations including input validation, output encoding, and strict URL validation mechanisms within the application's content processing pipeline. The recommended approach involves implementing a whitelist-based URL filtering system that only permits access to predetermined trusted domains while maintaining proper session management and user authentication controls. Additionally, developers should consider implementing secure coding practices that enforce proper access control checks at every point where external content is processed or displayed. Organizations should also establish regular security auditing procedures to identify and remediate similar access control vulnerabilities across their mobile application portfolios. The vulnerability highlights the importance of mobile application security in protecting user data and maintaining trust relationships between users and service providers, particularly in content management systems where user-generated content creates additional attack surface areas that require robust security controls.