Wallet security failures rarely look like a single dramatic “hack.”
More often, they’re small mistakes that line up: a seed phrase briefly hits a log, an approval screen hides what’s being signed, a nonce can be reused, or a browser context keeps a sensitive object alive longer than you assumed. Each issue seems minor in isolation. Together, they become the incident.
This article is a practical guide to auditing wallet code. It focuses on the vulnerabilities that show up repeatedly in production wallets, especially non-custodial mobile and browser wallets, and on what to verify in code, not what to “hope” the platform does for you.
What “wallet security” actually means in code review
A wallet code audit is not just a crypto review. It’s a review of how sensitive material flows through your app, how you decide what the user is signing, and how your software behaves when attackers control inputs.
In practice, a wallet audit usually touches four domains:
- Secret handling: key material, mnemonics, signing capability, and how these move through memory, storage, and logs (OWASP MASVS frames this as secure storage and preventing leakage).
- Signing safety: preventing replay, preventing ambiguous approvals, and ensuring that what gets signed is what the user saw.
- Provider and permission surface: how dapps connect, what they can request, and how phishing is prevented (EIP proposals increasingly emphasize phishing risk in permission requests).
- Dependency and runtime risk: browser extension contexts, mobile OS behavior, crash reporting, analytics, and third-party SDKs.
If you keep those domains separate while auditing, reviews become faster and more decisive. You stop arguing about “security in general” and start checking concrete failure modes.
Sensitive material leaks through boring places
Most wallet breaches don’t require breaking cryptography. They require finding where secrets pass through systems that were never designed to hold them.
Secrets stored locally without a clear protection boundary
A common failure pattern is “it’s encrypted somewhere” with no clarity on when the plaintext exists. OWASP MASVS explicitly calls out two requirements that map cleanly to wallets: securely store sensitive data and prevent leakage through platform features or misuse of APIs.
During an audit, look for where the mnemonic, seed, private keys, and extended keys are stored, and whether the storage boundary is enforced consistently across platforms. If you support both iOS and Android, verify that “secure storage” isn’t only true on one platform while the other falls back to an app database or preferences.
Logs, crash reports, and analytics quietly capture secrets
Wallets often leak through tooling rather than through business logic. Logging “helpful debug context” is a known source of secret exposure; some security best practice writeups call logs out as a common leak vector for wallet apps.
In a code audit, search aggressively for any stringification of sensitive values. Pay extra attention to “error wrappers” that attach request payloads, transaction objects, or decoded messages. Also, check crash reporting breadcrumbs and analytics events. If the team relies on “we only log in dev,” verify that dev builds aren’t shipped through beta channels, and that logs are still scrubbed in test environments.
Clipboard and screenshot paths that turn into extraction channels
Wallet UX often encourages copying. Attackers love that. Clipboard monitoring malware exists and is frequently discussed as a wallet risk, including the ability to replace copied addresses or capture seeds.
In audits, look for any flows that put mnemonics, private keys, or raw signed payloads into the clipboard, share sheets, screenshots, or exported files. The safest pattern is to design flows that never require copying secrets. When that’s unavoidable, the code should treat it as an exception, with warnings and guardrails.
Signing is where many “safe wallets” fail
Users don’t get drained because a wallet can sign. They get drained because a wallet signed the wrong thing, or because a signature can be reused.
Replay attacks caused by weak message binding
If your wallet supports message signing for authentication or approvals, check that signatures are bound to the intended domain, chain, and contract context. Typed structured data signing (EIP-712) exists largely to reduce ambiguity and prevent cross-domain signature collisions by using a domain separator.
In practice, audits should verify that the signed payload includes a nonce or unique identifier, that it includes chain context, and that the verifier side enforces those fields. For patterns like “permit” (EIP-2612 style), nonces and domain separators are a primary replay defense, and misunderstandings here have produced real failures over time.
Blind signing and approvals that hide what’s actually happening
“Blind signing” is a persistent wallet risk: users approve transactions without seeing meaningful details. Ledger describes blind signing as approving a transaction without understanding the full details, comparing it to signing a blank check.
An audit should review the signing UI path as carefully as the cryptography. The question is not “does the user see some data,” it’s “does the user see the right decision data.” For transactions, that means destination, value, token approvals, spender address, and any contract method effects you can safely display. For message signing, that means showing the domain, purpose, and whether the signature could authorize a transfer or approval.
Transaction simulation and decoding as a safety control
Many modern wallets mitigate blind signing with transaction simulation and human-readable decoding. Security vendors argue that transaction verification and simulation significantly improve software wallet safety by letting users review effects before signing.
In audits, treat simulation as a security feature with its own attack surface. Verify that simulations are clearly labeled as estimates, that you handle chain mismatches safely, and that simulation results don’t override raw transaction truth. Also, ensure simulation failures degrade safely, rather than silently falling back to blind approvals.
Dapp connection and permission prompts are a phishing surface
Even if your key storage is perfect, a wallet can still lose users’ funds by approving malicious requests. Phishing is mostly about interface and policy.
Overbroad permissions that users can’t meaningfully understand
Permissions are moving toward standardization because wallets need to communicate risk. EIP-7715 explicitly discusses phishing attacks where malicious dapps trick users into granting broad permissions, and it states that wallets must clearly display permissions and warn against dangerous grants.
In audits, review how your wallet scopes permissions by site origin and how it communicates them. If your wallet supports “connect once, sign forever,” check that it still requires explicit approval for high-impact actions like token approvals or contract interactions. Also, review whether the “connected site” view is visible and revocable in a few clicks.
Origin binding and UI consistency across webviews and deep links
Many real phishing incidents succeed because the user can’t reliably tell which site is requesting a signature. That’s especially true when wallets embed dapp browsers or support deep links. Security teams have highlighted WalletConnect phishing risks when integrated into wallets without strict domain handling.
Audit how you display the requesting origin. Confirm it comes from a trusted source, not from user-provided metadata. Verify that the origin displayed on the approval screen matches the origin used for permission decisions. Inconsistencies here create a situation where the wallet “thinks” it is authorizing site A while the UI suggests site B.
Extension and mobile runtime issues that break security assumptions
Wallet code often runs in constrained, fragmented runtimes. These runtimes can create security gaps unless your architecture accounts for them.
Browser extension isolation and message passing mistakes
Extension wallets depend heavily on content scripts, injected providers, and message passing. A common class of issues is insufficient validation of messages crossing the boundary between page context and extension context. If the extension treats page-supplied inputs as trusted, it can enable request forgery or privilege escalation inside the wallet.
In audits, trace the message path end-to-end. Confirm that every inbound request is validated against an allowlist of methods, that parameters are parsed strictly, and that approvals are bound to the exact request payload the user reviewed.
Mobile OS behaviors that create accidental persistence
Mobile platforms can snapshot screens, keep caches, and persist data in unexpected places. OWASP’s storage and leakage guidance exists because these behaviors are normal, not exotic.
In audits, look for secrets appearing in UI text fields, webviews, or screenshotable screens. Check that sensitive views aren’t being captured in app switcher previews where possible. Also, review how the app behaves after crashes and restarts: does it return to a locked state, or does it restore sensitive context too eagerly?
Dependency and update risk are part of wallet security
Wallets are security products built on large dependency graphs. That’s not inherently bad, but it changes what “audit” means.
Third-party libraries that touch keys, signing, or transports
Any library that handles keys, signing, or device transports becomes part of your security boundary. LedgerJS, for example, abstracts hardware wallet transports across environments. If you integrate such tooling, audit how you handle device errors, user approvals, and “blind signing” toggles, not just the calls themselves.
Also, audit how you pin versions, how you review updates, and how you respond to upstream security advisories. A wallet that auto-updates dependencies without review can inherit vulnerabilities in places users can’t see.
Build configuration and “debug features” shipping by accident
Audits should include build-time behavior: debug flags, verbose logs, test seeds, mock endpoints, and developer-only screens. Wallet security incidents have involved users being tricked into entering seed phrases into fake applications and interfaces, often using “support” flows as the lure.
Your code should make it hard to ship dangerous debug features. If a build allows exporting secrets, it should be clearly segregated and protected, and ideally, impossible to enable in production builds.
A practical audit workflow that teams can repeat
Wallet audits feel overwhelming when they’re treated as a single pass. They become manageable when you run them in layers, each with a clear goal.
Start with a data-flow map of sensitive material
Before reading line-by-line, map where sensitive data can exist: mnemonic input, key derivation, signing, storage, clipboard, logs, and network boundaries. Then, verify each boundary is enforced. MASVS storage guidance provides a useful mental model: secure intentional storage and prevent unintentional leakage.
Treat signing surfaces as security-critical UI
Audit every path that leads to signMessage, signTypedData, and sendTransaction. Focus on what the user sees and what the wallet actually signs. Blind signing risk is as much UX as it is cryptography.
Test replay and origin confusion intentionally
Create internal test cases where signatures are reused, nonces are repeated, chain IDs change, and origins are spoofed. EIP-712 domain separator expectations and the phishing warnings in permission proposals exist because these are real attack patterns, not theoretical ones.
Verify failure paths as carefully as success paths
Attackers live in error handling. Check what happens when RPC calls time out, when hardware wallets disconnect, when simulation fails, and when decoding fails. Confirm that the wallet fails closed on sensitive actions, rather than falling back to weaker behavior.
Conclusion
Auditing wallet code is less about “finding one bug” and more about proving your safety boundaries hold under real conditions. The repeat offenders are consistent: sensitive material leaking through storage or logs (the exact risks OWASP MASVS storage and leakage requirements target), signing flows that hide intent or allow replay, and permission prompts that enable phishing.
If your audit process keeps returning to the same questions, you’ll catch the vulnerabilities that matter most, before attackers do.
