validOffsets := and(
    validOffsets,
    eq(
        // Load signature offset from calldata 0x244.
        calldataload(BasicOrder_signature_cdPtr),
        // Derive expected offset as start of recipients + len * 64.
        add(
            BasicOrder_signature_ptr,
            mul(
                // Additional recipients length at calldata 0x264.
                calldataload(
                    BasicOrder_additionalRecipients_length_cdPtr
                ),
                // Each additional recipient has a length of 0x40.
                AdditionalRecipients_size
            )
        )
    )
modified   test/index.js
@@ -15945,6 +15945,25 @@ describe(`Consideration (version: ${VERSION})  initial test suite`, function
         ).to.be.revertedWith("InvalidBasicOrderParameterEncoding");
       });
 
+      it("Malicious calldata", async () => {
+        console.log(`Good data: ${calldata}`)
+        console.log(`calldata[0x284:0x2a4]: ${calldata.slice(2 * 0x284 + 2, 2 * 0x2a4 + 2)}`)
+        const badData = [calldata.slice(0, 2 * 0x284 + 2), "f000000000000000000000000000000000000000000000000000000000000000", calldata.slice(2 * 0x2a4 + 2)].join(
+          ""
+        );
+        console.log(`Bad data: ${badData}`)
+        expect(badData.length).to.eq(calldata.length);
+
+        await expect(
+          buyer.sendTransaction({
+            to: marketplaceContract.address,
+            data: badData,
+            value,
+          })
+        ).to.be.revertedWith("InvalidBasicOrderParameterEncoding");
+      });
+
       it("Reverts if additionalRecipients has non-default offset", async () => {
         const badData = [
