Microsoft researchers found a critical flaw in EngageSDK that lets apps bypass Android sandbox protections and access private data. The flaw put millions of users, including over 30M crypto wallet installs, at risk.
Developers fixed it in version 5.2.1 after coordinated disclosure, and vulnerable apps were removed from Google Play. The good news is that no active exploitation has been confirmed, but the case highlights risks from third-party SDKs widely used in mobile apps.
“As mobile wallets and other high‑value apps become more common, even small flaws in upstream libraries can impact millions of devices. These risks increase when integrations expose exported components or rely on trust assumptions that aren’t validated across app boundaries.” reads the report published by Microsoft.
“Because Android apps frequently depend on external libraries, insecure integrations can introduce attack surfaces into otherwise secure applications.”
Android protects apps by isolating them with unique IDs, private storage, and controlled communication through intents. The EngageLab SDK flaw breaks this protection using an intent redirection issue.
“Intent Redirection occurs when a threat actor manipulates the contents of an intent that a vulnerable app sends using its own identity and permissions.
In this scenario, the threat actor leverages the trusted context of the affected app to run a malicious payload with the app’s privileges.” continues the report. “This can lead to:
A malicious app can send a crafted intent to a vulnerable app, which then processes it and unknowingly sends a new intent with its own permissions. This allows the attacker to act with higher privileges.
The problem comes from an exported component called MTCommonActivity, automatically added during the build process. Many developers miss it because it only appears in the merged app configuration. Since it is exported, any app on the device can interact with it. This component reads attacker-controlled data and builds a new intent, but instead of keeping it safe, it creates a targeted intent that directly calls internal components.
The flaw becomes more dangerous because it uses unsafe flags that grant read and write access to data. Once triggered, the attacker can access private files through the app’s content providers, even if those were not meant to be exposed.
In simple terms, this vulnerability lets one app trick another into opening its doors, giving access to sensitive data and bypassing Android’s core security protections.
Many affected apps belong to the crypto and digital wallet ecosystem, making the flaw particularly severe. Microsoft confirmed the issue in multiple Google Play apps before disclosure. Wallet apps alone reached over 30 million installs, while total exposure across all affected apps exceeded 50 million.
Microsoft discovered the vulnerability in EngageLab SDK v4.5.4 and reported it in April 2025, later involving the Android Security Team in May due to Play Store impact. EngageLab fixed the issue in version 5.2.1, released on November 3, 2025, by making the vulnerable component non-exported, blocking access from other apps.
“To keep your apps secure, always review the merged Android manifest, especially when you incorporate third‑party SDKs. This helps you identify any components or permissions that might affect your app’s security or behavior.” concludes Microsoft.
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