Silent SDK Auto-Update (Post-Deploy Behavior Change)

← Supply Chain (OWASP Mobile M2)

silent_sdk_auto_update   HARD

Description

A benign-looking SDK silently fetches and swaps in new behavior at runtime (SpinOK-style), turning malicious after install with no app update or review.

How it works

A benign-looking analytics/ads SDK ships inside the app and passes store review serving only ads. At runtime it silently fetches a new “behavior descriptor” from its server and applies it without verifying any signature or checksum, the SpinOK-style pattern where a library turns malicious after install, with no new app version and no store re-review. Once the malicious descriptor lands, the same unchanged binary begins exfiltrating device contacts and the auth token. This is an offline, deterministic simulation: the “remote” is a local Map. The secure contrast requires a valid signature before applying any update, so the unsigned payload is rejected and behavior stays benign.

How to exercise it. DVMA is the harness - open this module from the home index and tap the demo action. The screen ships the malicious input and simulates the attacker (e.g. the companion app, crafted intent, or scanned payload) in-process, and the evidence panel prints the proof. The Tools (optional) and Attack inputs below are only needed to reproduce the exploit end-to-end on a real device.

Exploit steps

1. Set up. Build DVMA with a flavor that enables the Supply Chain (OWASP Mobile M2) category (e.g. --dart-define-from-file=config/flavors/dev.json) and run on an emulator/simulator you control. The demo needs no external tooling; for the optional on-device reproduction the relevant tools are: jadx, apktool.
2. Locate the target. From the home index, open Silent SDK Auto-Update (Post-Deploy Behavior Change) (silent_sdk_auto_update). The How it works section above describes this module’s specific weakness; the screen states the intended-secure behavior and exposes the vulnerable action.
3. Exploit. Inspect the dependency/SDK surface (lockfiles, bundled SDKs, update channel) and confirm the untrusted or unverified component is accepted - e.g. a substituted package, an unsigned artifact, or a silent post-deploy update.
4. Observe the evidence. Trigger the vulnerable action and read the evidence panel - it prints the concrete proof (leaked value, accepted replay, executed payload, or unauthorized result).
5. Contrast with the secure path. Run the module’s secure/hardened action (where provided) and confirm the same attack is rejected - this is what a correct implementation should do.

Tools (optional)

• jadx
• apktool