security: clear decrypted secrets after use (best-effort)

src/popup/views/confirmTx.js

@@ -334,8 +334,13 @@ function init(ctx) {
                 tx = await contract.transfer(pendingTx.to, amount);
             }
 
+            // Best-effort: clear decrypted secret after use.
+            // Note: JS strings are immutable; this nulls the reference but
+            // the original string may persist in memory until GC.
+            decryptedSecret = null;
             txStatus.showWait(pendingTx, tx.hash);
         } catch (e) {
+            decryptedSecret = null;
             const hash = tx ? tx.hash : null;
             txStatus.showError(pendingTx, hash, e.shortMessage || e.message);
         }