fix: validate destination address on send view

- Validate Ethereum addresses (0x + 40 hex chars) and ENS names
- EIP-55 checksum validation for mixed-case addresses
- Block sending to zero address (0x0000...0000)
- Warn when sending to own address (allow but show warning)
- Inline error messages with reserved space (no layout shift)
- Disable Review button while address is invalid

Closes #67

src/popup/index.html

@@ -422,6 +422,11 @@
                         class="border border-border p-1 w-full font-mono text-sm bg-bg text-fg"
                         placeholder="Address (0x...) or ENS name"
                     />
+                    <div
+                        id="send-to-error"
+                        class="text-xs"
+                        style="min-height: 1.25rem; color: #cc0000"
+                    ></div>
                 </div>
                 <div class="mb-2">
                     <div class="flex justify-between mb-1">
@@ -637,16 +642,9 @@
                 <div class="flex justify-center mb-3">
                     <canvas id="receive-qr"></canvas>
                 </div>
-                <div
+                <div class="border border-border p-2 break-all mb-3 text-xs">
-                    id="receive-ens"
+                    <span id="receive-dot"></span>
-                    class="font-bold mb-1 hidden flex items-center"
+                    <span id="receive-address" class="select-all"></span>
-                ></div>
-                <div
-                    class="border border-border p-2 break-all mb-3 text-xs cursor-pointer"
-                    title="Click to copy"
-                >
-                    <span id="receive-address-dot"></span>
-                    <span id="receive-address-full"></span>
                     <span id="receive-etherscan-link"></span>
                 </div>
                 <button

src/popup/views/addressToken.js

@@ -12,7 +12,7 @@ const {
     balanceLine,
 } = require("./helpers");
 const { state, currentAddress, saveState } = require("../../shared/state");
-const { TOKEN_BY_ADDRESS, resolveSymbol } = require("../../shared/tokenList");
+const { TOKEN_BY_ADDRESS } = require("../../shared/tokenList");
 const {
     formatUsd,
     getPrice,
@@ -96,11 +96,14 @@ function show() {
         const tb = (addr.tokenBalances || []).find(
             (t) => t.address.toLowerCase() === tokenId.toLowerCase(),
         );
-        symbol = resolveSymbol(
+        const tracked = (state.trackedTokens || []).find(
-            tokenId,
+            (t) => t.address.toLowerCase() === tokenId.toLowerCase(),
-            addr.tokenBalances,
-            state.trackedTokens,
         );
+        symbol =
+            (tb && tb.symbol) ||
+            (tracked && tracked.symbol) ||
+            (knownToken && knownToken.symbol) ||
+            "?";
         amount = tb ? parseFloat(tb.balance || "0") : 0;
         price = getPrice(symbol);
     }

src/popup/views/receive.js

@@ -1,10 +1,4 @@
-const {
+const { $, showView, showFlash, addressDotHtml } = require("./helpers");
-    $,
-    showView,
-    showFlash,
-    addressDotHtml,
-    escapeHtml,
-} = require("./helpers");
 const { state, currentAddress } = require("../../shared/state");
 const QRCode = require("qrcode");
 
@@ -18,17 +12,8 @@ const EXT_ICON =
 function show() {
     const addr = currentAddress();
     const address = addr ? addr.address : "";
-    $("receive-address-dot").innerHTML = address ? addressDotHtml(address) : "";
+    $("receive-dot").innerHTML = address ? addressDotHtml(address) : "";
-    $("receive-address-full").textContent = address;
+    $("receive-address").textContent = address;
-    $("receive-address-full").dataset.full = address;
-    const ensName = addr ? addr.ensName || null : null;
-    const ensEl = $("receive-ens");
-    if (ensName) {
-        ensEl.innerHTML = addressDotHtml(address) + escapeHtml(ensName);
-        ensEl.classList.remove("hidden");
-    } else {
-        ensEl.classList.add("hidden");
-    }
     const link = address ? `https://etherscan.io/address/${address}` : "";
     $("receive-etherscan-link").innerHTML = link
         ? `<a href="${link}" target="_blank" rel="noopener" class="inline-flex items-center">${EXT_ICON}</a>`
@@ -65,16 +50,8 @@ function show() {
 }
 
 function init(ctx) {
-    $("receive-address-full").addEventListener("click", () => {
-        const addr = $("receive-address-full").dataset.full;
-        if (addr) {
-            navigator.clipboard.writeText(addr);
-            showFlash("Copied!");
-        }
-    });
-
     $("btn-receive-copy").addEventListener("click", () => {
-        const addr = $("receive-address-full").dataset.full;
+        const addr = $("receive-address").textContent;
         if (addr) {
             navigator.clipboard.writeText(addr);
             showFlash("Copied!");

src/popup/views/send.js

@@ -10,7 +10,108 @@ const {
 const { state, currentAddress } = require("../../shared/state");
 let ctx;
 const { getProvider } = require("../../shared/balances");
-const { KNOWN_SYMBOLS, resolveSymbol } = require("../../shared/tokenList");
+const { KNOWN_SYMBOLS, TOKEN_BY_ADDRESS } = require("../../shared/tokenList");
+const { getAddress } = require("ethers");
+
+const ZERO_ADDRESS = "0x0000000000000000000000000000000000000000";
+
+/**
+ * Validate a destination address string.
+ * Returns { valid: true } or { valid: false, error: "..." }.
+ */
+function validateToAddress(value) {
+    const v = value.trim();
+    if (!v) return { valid: false, error: "" };
+
+    // ENS names: contains a dot and doesn't start with 0x
+    if (v.includes(".") && !v.startsWith("0x")) {
+        // Basic ENS format check: at least one label before and after dot
+        if (/^[a-zA-Z0-9-]+(\.[a-zA-Z0-9-]+)+$/.test(v)) {
+            return { valid: true };
+        }
+        return {
+            valid: false,
+            error: "Please enter a valid ENS name.",
+        };
+    }
+
+    // Must look like an Ethereum address
+    if (!/^0x[0-9a-fA-F]{40}$/.test(v)) {
+        return {
+            valid: false,
+            error: "Please enter a valid Ethereum address.",
+        };
+    }
+
+    // Reject zero address
+    if (v.toLowerCase() === ZERO_ADDRESS) {
+        return {
+            valid: false,
+            error: "Sending to the zero address is not allowed.",
+        };
+    }
+
+    // EIP-55 checksum validation: all-lowercase is ok, otherwise must match checksum
+    if (v !== v.toLowerCase()) {
+        try {
+            const checksummed = getAddress(v);
+            if (checksummed !== v) {
+                return {
+                    valid: false,
+                    error: "Address checksum is invalid. Please double-check the address.",
+                };
+            }
+        } catch {
+            return {
+                valid: false,
+                error: "Address checksum is invalid. Please double-check the address.",
+            };
+        }
+    }
+
+    // Warn if sending to own address
+    const addr = currentAddress();
+    if (addr && v.toLowerCase() === addr.address.toLowerCase()) {
+        // Allow but will warn — we return valid with a warning
+        return {
+            valid: true,
+            warning: "This is your own address. Are you sure?",
+        };
+    }
+
+    return { valid: true };
+}
+
+function updateToValidation() {
+    const input = $("send-to");
+    const errorEl = $("send-to-error");
+    const btn = $("btn-send-review");
+    const value = input.value.trim();
+
+    if (!value) {
+        errorEl.textContent = "";
+        btn.disabled = true;
+        btn.classList.add("opacity-50");
+        return;
+    }
+
+    const result = validateToAddress(value);
+    if (!result.valid) {
+        errorEl.textContent = result.error;
+        errorEl.style.color = "#cc0000";
+        btn.disabled = true;
+        btn.classList.add("opacity-50");
+    } else if (result.warning) {
+        errorEl.textContent = result.warning;
+        errorEl.style.color = "#b8860b";
+        btn.disabled = false;
+        btn.classList.remove("opacity-50");
+    } else {
+        errorEl.textContent = "";
+        btn.disabled = false;
+        btn.classList.remove("opacity-50");
+    }
+}
 
 const EXT_ICON =
     `<span style="display:inline-block;width:10px;height:10px;margin-left:4px;vertical-align:middle">` +
@@ -73,11 +174,15 @@ function updateSendBalance() {
         const tb = (addr.tokenBalances || []).find(
             (t) => t.address.toLowerCase() === token.toLowerCase(),
         );
-        const symbol = resolveSymbol(
+        const knownToken = TOKEN_BY_ADDRESS.get(token.toLowerCase());
-            token,
+        const tracked = (state.trackedTokens || []).find(
-            addr.tokenBalances,
+            (t) => t.address.toLowerCase() === token.toLowerCase(),
-            state.trackedTokens,
         );
+        const symbol =
+            (tb && tb.symbol) ||
+            (tracked && tracked.symbol) ||
+            (knownToken && knownToken.symbol) ||
+            "?";
         const bal = tb ? tb.balance || "0" : "0";
         $("send-balance").textContent =
             "Current balance: " + bal + " " + symbol;
@@ -88,6 +193,13 @@ function init(_ctx) {
     ctx = _ctx;
     $("send-token").addEventListener("change", updateSendBalance);
 
+    // Initial state: disable review button until address is entered
+    $("btn-send-review").disabled = true;
+    $("btn-send-review").classList.add("opacity-50");
+
+    // Validate address on input
+    $("send-to").addEventListener("input", updateToValidation);
+
     $("btn-send-review").addEventListener("click", async () => {
         const to = $("send-to").value.trim();
         const amount = $("send-amount").value.trim();
@@ -95,6 +207,15 @@ function init(_ctx) {
             showFlash("Please enter a recipient address.");
             return;
         }
+
+        // Re-validate before proceeding
+        const validation = validateToAddress(to);
+        if (!validation.valid) {
+            showFlash(
+                validation.error || "Please enter a valid Ethereum address.",
+            );
+            return;
+        }
         if (!amount || isNaN(parseFloat(amount)) || parseFloat(amount) <= 0) {
             showFlash("Please enter a valid amount.");
             return;
@@ -128,11 +249,15 @@ function init(_ctx) {
             const tb = (addr.tokenBalances || []).find(
                 (t) => t.address.toLowerCase() === token.toLowerCase(),
             );
-            tokenSymbol = resolveSymbol(
+            const knownTk = TOKEN_BY_ADDRESS.get(token.toLowerCase());
-                token,
+            const trackedTk = (state.trackedTokens || []).find(
-                addr.tokenBalances,
+                (t) => t.address.toLowerCase() === token.toLowerCase(),
-                state.trackedTokens,
             );
+            tokenSymbol =
+                (tb && tb.symbol) ||
+                (trackedTk && trackedTk.symbol) ||
+                (knownTk && knownTk.symbol) ||
+                "?";
             tokenBalance = tb ? tb.balance || "0" : "0";
         }
 

src/shared/tokenList.js

@@ -3645,27 +3645,10 @@ async function getTopTokenPrices(n) {
     return prices;
 }
 
-// Resolve a token symbol from multiple sources, never returning "?".
-function resolveSymbol(tokenAddress, tokenBalances, trackedTokens) {
-    const lower = (tokenAddress || "").toLowerCase();
-    const tb = (tokenBalances || []).find(
-        (t) => t.address.toLowerCase() === lower,
-    );
-    if (tb && tb.symbol) return tb.symbol;
-    const known = TOKEN_BY_ADDRESS.get(lower);
-    if (known && known.symbol) return known.symbol;
-    const tracked = (trackedTokens || []).find(
-        (t) => t.address.toLowerCase() === lower,
-    );
-    if (tracked && tracked.symbol) return tracked.symbol;
-    return lower.slice(0, 10) + "\u2026";
-}
-
 module.exports = {
     TOKENS,
     TOKEN_BY_ADDRESS,
     KNOWN_SYMBOLS,
     getTopTokens,
     getTopTokenPrices,
-    resolveSymbol,
 };