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Introduction:
The European Union’s €2 million age verification app was designed to solve a genuinely difficult problem: allowing users to prove they are old enough to access a service without revealing unnecessary personal information. Built on zero-knowledge proof (ZKP) cryptography and positioned as a privacy-preserving cornerstone of the future European Digital Identity (EUDI) Wallet ecosystem, the app promised to reconcile privacy with enforcement. Yet within hours of its April 2026 launch, security researcher Paul Moore demonstrated a bypass in under two minutes. Three months and multiple updates later, Moore struck again—this time using an AI-generated Chrome extension to replay anonymous age proofs indefinitely. The fundamental question remains unanswered: How do you prove someone is over 18 without knowing who they are, while also ensuring that proof cannot be reused, replayed, or abused?
Learning Objectives:
- Understand the architectural tension between privacy-preserving zero-knowledge proofs and the enforcement requirements of age verification systems
- Analyze real-world vulnerabilities in the EU Age Verification App, including local file manipulation, biometric bypasses, and attestation replay attacks
- Learn practical security assessment techniques for digital identity wallets, including configuration file analysis, client-side control auditing, and protocol-level testing
You Should Know:
- The Anatomy of the Bypass: From Local File Edits to AI-Generated Extensions
The EU Age Verification App’s vulnerabilities fall into two distinct categories: client-side configuration weaknesses and fundamental architectural flaws.
April 2026 – The Two-Minute PIN Bypass: Moore demonstrated that the app stored an encrypted PIN in an editable local configuration file (shared_prefs/eudi-wallet.xml). By navigating to this file, deleting the encrypted PIN entries, and restarting the application, an attacker could set a new PIN and gain full access to existing verified credentials. The same configuration file controlled rate-limiting (a simple counter that could be reset) and biometric authentication (a single Boolean flag that could be toggled from `true` to false). No root access, no complex tools—just a file manager.
Android forensic analysis of the vulnerability Location of the configuration file: /data/data/[bash]/shared_prefs/eudi-wallet.xml Example of the vulnerable configuration entries: <map> <string name="encrypted_pin">[bash]</string> <int name="pin_attempt_count" value="3" /> <boolean name="biometric_enabled" value="true" /> </map> Attack vector: delete encrypted_pin entry, reset attempt_count to 0, set biometric_enabled to false, restart app, set new PIN
July 2026 – The Chrome Extension Replay Attack: Despite “three months of security hardening,” Moore bypassed version 2026.07-1 using a Chrome extension generated entirely by ClaudeAI “in a matter of minutes”. The extension intercepts and replays the anonymous age proof whenever a site requests verification. Because the app is designed to confirm only that a user is above a certain age while deliberately withholding personal information, the relying website never knows whether the proof belongs to the person actually at the keyboard. The “single-use” protection is client-enforced, meaning the server has no way to detect that the same attestation is being re-presented across multiple sessions.
Conceptual attack flow for attestation replay: 1. User completes legitimate age verification once 2. Chrome extension captures the valid "over 18" attestation token 3. Extension stores the token and replays it on demand 4. Each new site requesting verification receives the same valid proof 5. Verifier accepts the proof because it has no session-binding mechanism The core issue: the verifier has "absolutely no information" other than an "over 18" attestation, making replay detection impossible
- Zero-Knowledge Proofs: Privacy Gold Standard or Architectural Achilles’ Heel?
Zero-knowledge proofs (ZKPs) are cryptographic techniques that enable one party to prove a statement to another without revealing any information beyond the validity of the statement itself. In the context of age verification, the user’s application convinces a relying party of a single fact—“this user is over 18”—without revealing the user’s identity, date of birth, or any other attribute.
The EU Commission framed this as the “golden standard in privacy protection,” ensuring that “users’ data is safe and tracking is prevented”. Online platforms receive only confirmation that the user meets the required age threshold, and the link between the user and the proof provider is cut after issuance.
The Problem: This privacy guarantee creates an enforcement gap. As Moore observed, the verifier has “absolutely no information” other than an “over 18” attestation. The system cannot distinguish between a legitimate user presenting their own proof and an attacker replaying a captured attestation. The trust model hinges entirely on anonymous, reusable proofs with weak resistance to replay or automation.
From a security engineering standpoint, this is less a “bug” and more a structural mismatch between privacy requirements and enforcement needs. You cannot have both perfect anonymity and perfect accountability—every design choice involves trade-offs.
3. Open Source as a Double-Edged Sword
One major positive takeaway is that the project is open source. The code is publicly available on GitHub, allowing independent researchers to identify weaknesses, challenge assumptions, and improve the solution before large-scale adoption. EU officials explicitly embraced this transparency: “Why did we decide to have it open source: to be transparent and to allow, indeed, for the community, for developers to test it, to play with it, to potentially help us to improve it”.
The Reality: Open source enabled the very discoveries that exposed the app’s fragility. Within hours of the April launch, researchers began picking apart the code. By Thursday, Moore had demonstrated the bypass. The GitHub repository itself warns that this is a “demo version” with a lower security level than the final product and is “not intended to be used in production as-is”.
Yet the Commission had declared the app “technically ready” and meeting “the highest privacy standards in the world”. This disconnect between official positioning and the repository’s disclaimer highlights a critical governance challenge: how do you communicate the maturity of open-source reference implementations without undermining public trust?
4. Practical Security Assessment: Testing Digital Identity Wallets
For security professionals assessing similar digital identity systems, the EU Age Verification App provides valuable lessons in vulnerability discovery.
Step-by-Step Assessment Guide:
Step 1: Static Analysis of Client-Side Storage
- Examine all local storage locations (
shared_prefs/, databases, internal storage) - Look for hardcoded credentials, encryption keys, or sensitive data in plaintext
- Test whether modifying configuration values (PIN, biometric flags, rate limits) produces expected security failures
Step 2: Protocol Analysis
- The app uses OpenID4VP (remote presentation) and OpenID4VCI (issuing) protocols
- Test endpoints at the public demo services: Issuer (
https://issuer.ageverification.dev/`) and Verifier (https://verifier.ageverification.dev/`) - Intercept traffic between the wallet and relying parties to understand attestation format and validation logic
Step 3: Replay Attack Testing
- Capture a valid attestation presentation
- Attempt to replay the same attestation to the verifier across different sessions
- Test whether the verifier implements any nonce, timestamp, or session-binding mechanisms
Step 4: Client-Side Integrity Bypasses
- On Android: modify the APK, patch security checks, or use Frida for runtime instrumentation
- On iOS: examine the reference implementation at `eu-digital-identity-wallet/av-app-ios-wallet-ui`
– Test whether the system relies on client-side enforcement for critical security properties
Sample command to extract and examine the Android APK: $ adb shell pm list packages | grep age $ adb shell pm path [bash] $ adb pull [bash] ./app.apk $ unzip app.apk -d ./decompiled/ $ grep -r "encrypted_pin" ./decompiled/ $ grep -r "biometric" ./decompiled/ For iOS analysis (requires jailbreak or development build): Examine the Pin Storage Configuration Check for sequential or easily guessable patterns The app's own documentation warns: "Sequential or easily guessable patterns (such as '135246' or '147258') should not be permitted"
- The Broader EUDI Wallet Ecosystem: What’s at Stake
The age verification app is built on the same technical foundations as the forthcoming EU Digital Identity (EUDI) Wallets. Under eIDAS 2.0 (Regulation 2024/1183), every Member State must offer at least one EUDI Wallet by 6 December 2026. These wallets will handle far more sensitive functions than age verification: authentication, electronic signatures, identity verification for banking and government services.
The age verification app serves as a critical test case. If the Commission cannot get age verification right—a comparatively simple use case—what confidence should citizens have in the broader EUDI Wallet ecosystem? The vulnerabilities discovered in the AV app—local file manipulation, biometric bypasses, attestation replay—represent exactly the kinds of issues that could plague the full wallet implementation if not addressed at the architectural level.
The Commission’s Response: Officials have characterized the app as a demo version and emphasized that developers are listening to feedback. But Moore and French cryptographer Olivier Blazy pushed back, stating they were testing the latest version of the code when they found the flaws. The Commission later claimed the issues were fixed, but Moore’s July demonstration proved otherwise.
6. Hardening Recommendations for Digital Identity Systems
Based on the EU Age Verification App’s vulnerabilities, security architects should consider the following hardening measures:
For Local Storage:
- Store sensitive data (PINs, biometric references) in hardware-backed secure enclaves, not editable configuration files
- Implement server-side rate limiting; never trust client-side counters for security-critical functions
- Use Android’s Keystore or iOS’s Keychain with hardware-backed security for credential storage
For Attestation Protocols:
- Implement cryptographic binding between attestations, user sessions, and specific devices
- Use nonces or timestamps to prevent replay attacks—and verify them on the server
- Consider device attestation (Play Integrity, App Attest) to verify that the presenting client is genuine
For Zero-Knowledge Proof Systems:
- Evaluate whether the ZKP implementation provides unlinkability without sacrificing replay protection
- Consider hybrid models where ZKPs are combined with session-specific challenges
- Test replay resistance explicitly in security assessments
What Undercode Say:
- Key Takeaway 1: The EU Age Verification App’s fundamental flaw is architectural, not merely a bug that can be patched. Anonymous age verification—where the verifier receives only an “over 18” attestation with no user identity or session binding—cannot reliably prevent replay attacks. This is a structural tension between privacy and enforcement, not a coding error.
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Key Takeaway 2: Open source is a powerful accountability mechanism, but it requires honest communication about maturity. The Commission’s declaration that the app was “technically ready” while the GitHub repository warned against production use created a credibility gap. Transparency must extend to governance, not just code.
The most interesting part of this story isn’t the bypass itself. It’s the challenge behind it: How do you build digital identity systems that respect privacy while providing the accountability that enforcement requires? The EU Age Verification App represents an ambitious attempt at this balance—and its failures illuminate the genuinely hard engineering problems that remain unsolved.
Innovation isn’t about building perfect systems from day one. Sometimes, its greatest value lies in revealing where the truly hard engineering problems are. The EU’s open-source approach enabled independent researchers to identify weaknesses, challenge assumptions, and improve the solution before large-scale adoption. In many ways, this is exactly how resilient digital ecosystems are built: through continuous testing, scrutiny, and improvement.
Prediction:
- -1 The EU Age Verification App will face continued bypasses unless the architecture is fundamentally redesigned to include session binding or device attestation. Incremental patches cannot solve the underlying structural mismatch between anonymity and enforcement.
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-1 Public trust in the broader EUDI Wallet ecosystem will be eroded if the Commission continues to declare systems “technically ready” while known vulnerabilities remain unaddressed. The gap between official messaging and technical reality creates a credibility problem that will follow the wallet initiative for years.
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+1 The open-source, community-tested approach will ultimately produce a more robust system than closed, proprietary alternatives. Each bypass discovered now is a lesson that can be incorporated before the system is mandated for billions of European citizens.
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+1 The security research community’s scrutiny of the age verification app will force the Commission to adopt more rigorous security engineering practices, including formal threat modeling, red-team testing, and architectural reviews before future EUDI Wallet components are deployed.
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-1 If the Commission does not address the architectural flaw before the December 2026 EUDI Wallet mandate, we can expect a wave of similar bypasses targeting the full wallet implementation—with far more serious consequences than age verification failures.
▶️ Related Video (80% Match):
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Reported By: Sorin Ardelean – Hackers Feeds
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