feat: expand confirm-tx warnings — closes #114

- Refactor address warnings into src/shared/addressWarnings.js module
  - getLocalWarnings(address, options): sync checks against local lists
  - getFullWarnings(address, provider, options): async local + RPC checks
- Expand scam address list from 652 to 2417 addresses
  - Added EtherScamDB (MIT) as additional source
- Update confirmTx.js to use the new addressWarnings module

src/popup/index.html

@@ -605,6 +605,31 @@
                         Double-check the address before sending.
                     </div>
                 </div>
+                <div
+                    id="confirm-contract-warning"
+                    class="mb-2"
+                    style="visibility: hidden"
+                >
+                    <div
+                        class="border border-red-500 border-dashed p-2 text-xs font-bold text-red-500"
+                    >
+                        WARNING: The recipient is a smart contract. Sending ETH
+                        or tokens directly to a contract may result in permanent
+                        loss of funds.
+                    </div>
+                </div>
+                <div
+                    id="confirm-burn-warning"
+                    class="mb-2"
+                    style="visibility: hidden"
+                >
+                    <div
+                        class="border border-red-500 border-dashed p-2 text-xs font-bold text-red-500"
+                    >
+                        WARNING: This is a known null/burn address. Funds sent
+                        here are permanently destroyed and cannot be recovered.
+                    </div>
+                </div>
                 <div
                     id="confirm-errors"
                     class="mb-2 border border-border border-dashed p-2"

src/popup/views/confirmTx.js

@@ -25,8 +25,11 @@ const { getSignerForAddress } = require("../../shared/wallet");
 const { decryptWithPassword } = require("../../shared/vault");
 const { formatUsd, getPrice } = require("../../shared/prices");
 const { getProvider } = require("../../shared/balances");
-const { isScamAddress } = require("../../shared/scamlist");
-const { ERC20_ABI } = require("../../shared/constants");
+const {
+    getLocalWarnings,
+    getFullWarnings,
+} = require("../../shared/addressWarnings");
+const { ERC20_ABI, isBurnAddress } = require("../../shared/constants");
 const { log } = require("../../shared/log");
 const makeBlockie = require("ethereum-blockies-base64");
 const txStatus = require("./txStatus");
@@ -167,23 +170,17 @@ function show(txInfo) {
         $("confirm-balance").textContent = valueWithUsd(bal + " ETH", balUsd);
     }
 
-    // Check for warnings
-    const warnings = [];
-    if (isScamAddress(txInfo.to)) {
-        warnings.push(
-            "This address is on a known scam/fraud list. Do not send funds to this address.",
-        );
-    }
-    if (txInfo.to.toLowerCase() === txInfo.from.toLowerCase()) {
-        warnings.push("You are sending to your own address.");
-    }
+    // Check for warnings (synchronous local checks)
+    const localWarnings = getLocalWarnings(txInfo.to, {
+        fromAddress: txInfo.from,
+    });
 
     const warningsEl = $("confirm-warnings");
-    if (warnings.length > 0) {
-        warningsEl.innerHTML = warnings
+    if (localWarnings.length > 0) {
+        warningsEl.innerHTML = localWarnings
             .map(
                 (w) =>
-                    `<div class="border border-border border-dashed p-2 mb-1 text-xs font-bold">WARNING: ${w}</div>`,
+                    `<div class="border border-border border-dashed p-2 mb-1 text-xs font-bold">WARNING: ${w.message}</div>`,
             )
             .join("");
         warningsEl.style.visibility = "visible";
@@ -247,8 +244,15 @@ function show(txInfo) {
     state.viewData = { pendingTx: txInfo };
     showView("confirm-tx");
 
-    // Reset recipient warning to hidden (space always reserved, no layout shift)
+    // Reset async warnings to hidden (space always reserved, no layout shift)
     $("confirm-recipient-warning").style.visibility = "hidden";
+    $("confirm-contract-warning").style.visibility = "hidden";
+    $("confirm-burn-warning").style.visibility = "hidden";
+
+    // Show burn warning via reserved element (in addition to inline warning)
+    if (isBurnAddress(txInfo.to)) {
+        $("confirm-burn-warning").style.visibility = "visible";
+    }
 
     estimateGas(txInfo);
     checkRecipientHistory(txInfo);
@@ -295,19 +299,18 @@ async function estimateGas(txInfo) {
 }
 
 async function checkRecipientHistory(txInfo) {
-    const el = $("confirm-recipient-warning");
     try {
         const provider = getProvider(state.rpcUrl);
-        // Skip warning for contract addresses — they may legitimately
-        // have zero outgoing transactions (getTransactionCount returns
-        // the nonce, i.e. sent-tx count only).
-        const code = await provider.getCode(txInfo.to);
-        if (code && code !== "0x") {
-            return;
-        }
-        const txCount = await provider.getTransactionCount(txInfo.to);
-        if (txCount === 0) {
-            el.style.visibility = "visible";
+        const asyncWarnings = await getFullWarnings(txInfo.to, provider, {
+            fromAddress: txInfo.from,
+        });
+        for (const w of asyncWarnings) {
+            if (w.type === "contract") {
+                $("confirm-contract-warning").style.visibility = "visible";
+            }
+            if (w.type === "new-address") {
+                $("confirm-recipient-warning").style.visibility = "visible";
+            }
         }
     } catch (e) {
         log.errorf("recipient history check failed:", e.message);

src/shared/addressWarnings.js

@@ -0,0 +1,98 @@
+// Address warning module.
+// Provides local and async (RPC-based) warning checks for Ethereum addresses.
+// Returns arrays of {type, message, severity} objects.
+
+const { isScamAddress } = require("./scamlist");
+const { isBurnAddress } = require("./constants");
+const { log } = require("./log");
+
+/**
+ * Check an address against local-only lists (scam, burn, self-send).
+ * Synchronous — no network calls.
+ *
+ * @param {string} address - The target address to check.
+ * @param {object} [options] - Optional context.
+ * @param {string} [options.fromAddress] - Sender address (for self-send check).
+ * @returns {Array<{type: string, message: string, severity: string}>}
+ */
+function getLocalWarnings(address, options = {}) {
+    const warnings = [];
+    const addr = address.toLowerCase();
+
+    if (isScamAddress(addr)) {
+        warnings.push({
+            type: "scam",
+            message:
+                "This address is on a known scam/fraud list. Do not send funds to this address.",
+            severity: "critical",
+        });
+    }
+
+    if (isBurnAddress(addr)) {
+        warnings.push({
+            type: "burn",
+            message:
+                "This is a known null/burn address. Funds sent here are permanently destroyed and cannot be recovered.",
+            severity: "critical",
+        });
+    }
+
+    if (options.fromAddress && addr === options.fromAddress.toLowerCase()) {
+        warnings.push({
+            type: "self-send",
+            message: "You are sending to your own address.",
+            severity: "warning",
+        });
+    }
+
+    return warnings;
+}
+
+/**
+ * Check an address against local lists AND via RPC queries.
+ * Async — performs network calls to check contract status and tx history.
+ *
+ * @param {string} address - The target address to check.
+ * @param {object} provider - An ethers.js provider instance.
+ * @param {object} [options] - Optional context.
+ * @param {string} [options.fromAddress] - Sender address (for self-send check).
+ * @returns {Promise<Array<{type: string, message: string, severity: string}>>}
+ */
+async function getFullWarnings(address, provider, options = {}) {
+    const warnings = getLocalWarnings(address, options);
+
+    try {
+        const code = await provider.getCode(address);
+        if (code && code !== "0x") {
+            warnings.push({
+                type: "contract",
+                message:
+                    "This address is a smart contract, not a regular wallet.",
+                severity: "warning",
+            });
+            // If it's a contract, skip the tx count check — contracts
+            // may legitimately have zero inbound EOA transactions.
+            return warnings;
+        }
+    } catch (e) {
+        log.errorf("contract check failed:", e.message);
+    }
+
+    try {
+        const txCount = await provider.getTransactionCount(address);
+        if (txCount === 0) {
+            warnings.push({
+                type: "new-address",
+                message:
+                    "This address has never sent a transaction. Double-check it is correct.",
+                severity: "info",
+            });
+        }
+    } catch (e) {
+        log.errorf("tx count check failed:", e.message);
+    }
+
+    return warnings;
+}
+
+module.exports = { getLocalWarnings, getFullWarnings };

src/shared/constants.js

@@ -20,6 +20,19 @@ const ERC20_ABI = [
     "function approve(address spender, uint256 amount) returns (bool)",
 ];
 
+// Known null/burn addresses that permanently destroy funds.
+const BURN_ADDRESSES = new Set([
+    "0x0000000000000000000000000000000000000000",
+    "0x0000000000000000000000000000000000000001",
+    "0x000000000000000000000000000000000000dead",
+    "0xdead000000000000000000000000000000000000",
+    "0x00000000000000000000000000000000deadbeef",
+]);
+
+function isBurnAddress(address) {
+    return BURN_ADDRESSES.has(address.toLowerCase());
+}
+
 module.exports = {
     DEBUG,
     DEBUG_MNEMONIC,
@@ -28,4 +41,6 @@ module.exports = {
     DEFAULT_BLOCKSCOUT_URL,
     BIP44_ETH_PATH,
     ERC20_ABI,
+    BURN_ADDRESSES,
+    isBurnAddress,
 };