diff --git a/BUG_REPORT_name_reverse_lookup_poison.md b/BUG_REPORT_name_reverse_lookup_poison.md
new file mode 100644
index 0000000..5777240
--- /dev/null
+++ b/BUG_REPORT_name_reverse_lookup_poison.md
@@ -0,0 +1,106 @@
+# Bug: GitlawbNameRegistry — reverse-lookup poisoning via unchecked `register`
+
+**Severity**: MEDIUM — identity-confusion / phishing surface, not direct loss of funds.
+
+**Affected**: `src/GitlawbNameRegistry.sol`, functions `register(string, string)` and `update(string, string)`
+
+## Root cause
+
+`register()` writes the `didToName` reverse mapping without checking whether the DID is already mapped to another name :
+
+```solidity
+function register(string calldata name, string calldata did) external {
+    _validateName(name);
+    bytes32 nameHash = keccak256(bytes(name));
+    if (_records[nameHash].owner != address(0)) revert NameTaken(nameHash);
+
+    _records[nameHash] = NameRecord({...});
+
+    // Reverse mapping — silently overwrites
+    bytes32 didHash = keccak256(bytes(did));
+    didToName[didHash] = name;                          // ← no check
+    
+    emit NameRegistered(name, did, msg.sender, block.timestamp);
+}
+```
+
+`update()` has the same issue : it deletes the OLD didToName entry but blindly overwrites if the NEW DID is already mapped to another name.
+
+## Attack: identity confusion / phishing
+
+1. Alice registers `name="alice"`, `did="did:key:z6MkAliceKey..."`
+2. `didToName[keccak256(did:key:z6MkAliceKey...)]` = "alice" ✓
+3. Bob, attacker, registers `name="alice-prime"` with `did="did:key:z6MkAliceKey..."` (Alice's DID)
+4. Contract accepts — no check on reverse mapping
+5. `didToName[keccak256(did:key:z6MkAliceKey...)]` = "alice-prime" — Alice's reverse lookup is silently broken
+
+Any frontend/backend doing `reverseLookup(aliceDID)` returns Bob's chosen name. If Bob registers a phishing-flavored name (`alice-verified`, `alice-official`), apps display the wrong name when looking up Alice's DID.
+
+The FORWARD mapping `name → did` is fine for Alice (she still owns "alice"). But the REVERSE direction is poisoned.
+
+## Why this matters for Gitlawb
+
+The reverse mapping is **the canonical way** to display a name for a known DID. Gitlawb-skill agents will commonly call `reverseLookup(agentDid)` to know what to display when showing other agents in the UI. A poisoned mapping shows the attacker-chosen name → social engineering.
+
+## PoC
+
+```solidity
+function test_reverse_lookup_poisoning() public {
+    string memory aliceDid = "did:key:z6MkAlice...";
+
+    // Alice registers cleanly
+    vm.prank(alice);
+    nameRegistry.register("alice", aliceDid);
+    assertEq(nameRegistry.reverseLookup(aliceDid), "alice");
+
+    // Bob registers a different NAME but with Alice's DID
+    vm.prank(bob);
+    nameRegistry.register("alice-prime", aliceDid);
+
+    // Alice's reverse mapping is now poisoned
+    assertEq(nameRegistry.reverseLookup(aliceDid), "alice-prime"); // ← attacker wins
+}
+```
+
+## Suggested fix
+
+Add a check : the DID must not already have a reverse mapping when registering a new name, OR explicitly allow multiple names per DID (track as array).
+
+```solidity
+function register(string calldata name, string calldata did) external {
+    _validateName(name);
+    bytes32 nameHash = keccak256(bytes(name));
+    if (_records[nameHash].owner != address(0)) revert NameTaken(nameHash);
+
+    bytes32 didHash = keccak256(bytes(did));
++   // Forbid DID-squatting on the reverse mapping
++   if (bytes(didToName[didHash]).length != 0) revert DidAlreadyHasName(didHash);
+
+    _records[nameHash] = NameRecord({...});
+    didToName[didHash] = name;
+    emit NameRegistered(name, did, msg.sender, block.timestamp);
+}
+```
+
+Same in `update()` :
+
+```solidity
+function update(string calldata name, string calldata newDid) external {
+    ...
+    bytes32 newDidHash = keccak256(bytes(newDid));
++   if (bytes(didToName[newDidHash]).length != 0) revert DidAlreadyHasName(newDidHash);
+    didToName[newDidHash] = name;
+    ...
+}
+```
+
+## Secondary issues
+
+- `transfer()` doesn't validate `newOwner != address(0)` — accidental wipe possible
+- `transfer()` doesn't update `updatedAt` consistently with `update()`
+
+## Reporter
+
+@philpof102-svg — operator `0xAC3ca7c5d3cDD7702fd08F9C4C28dAA22296aDa9` (Base)
+MainStreet : https://avisradar-production.up.railway.app/mainstreet.html
+Related : [#5 (stranded rewards)](https://github.com/Gitlawb/contracts/pull/5), [#6 (claimBounty DoS)](https://github.com/Gitlawb/contracts/pull/6), [#7 (NodeStaking O(n) DoS)](https://github.com/Gitlawb/contracts/pull/7)
diff --git a/src/GitlawbNameRegistry.sol b/src/GitlawbNameRegistry.sol
index 2624b52..ecadd0b 100644
--- a/src/GitlawbNameRegistry.sol
+++ b/src/GitlawbNameRegistry.sol
@@ -38,6 +38,8 @@ contract GitlawbNameRegistry {
     error NotOwner(bytes32 nameHash, address caller);
     error NotRegistered(bytes32 nameHash);
     error InvalidName();
+    error DIDAlreadyClaimed(bytes32 didHash); // PR #8
+    error EmptyDID(); // PR #8
 
     // ── Functions ─────────────────────────────────────────────────────────────
 
@@ -46,9 +48,18 @@ contract GitlawbNameRegistry {
     /// @param did   Full DID string to associate with this name
     function register(string calldata name, string calldata did) external {
         _validateName(name);
+        if (bytes(did).length == 0) revert EmptyDID(); // PR #8 fix
         bytes32 nameHash = keccak256(bytes(name));
         if (_records[nameHash].owner != address(0)) revert NameTaken(nameHash);
 
+        // PR #8 fix : reject if this DID is already mapped to another name.
+        // Without this guard, an attacker can register "trusted-name-phish"
+        // pointing at the same DID a legitimate name owns, overwriting the
+        // didToName reverse mapping and turning consumers' reverseLookup(did)
+        // into a phishing surface.
+        bytes32 didHash = keccak256(bytes(did));
+        if (bytes(didToName[didHash]).length != 0) revert DIDAlreadyClaimed(didHash);
+
         _records[nameHash] = NameRecord({
             owner: msg.sender,
             did: did,
@@ -56,8 +67,6 @@ contract GitlawbNameRegistry {
             updatedAt: block.timestamp
         });
 
-        // Reverse mapping
-        bytes32 didHash = keccak256(bytes(did));
         didToName[didHash] = name;
 
         emit NameRegistered(name, did, msg.sender, block.timestamp);
@@ -65,20 +74,30 @@ contract GitlawbNameRegistry {
 
     /// Update the DID associated with a name. Only the current owner can call.
     function update(string calldata name, string calldata newDid) external {
+        if (bytes(newDid).length == 0) revert EmptyDID(); // PR #8 fix
         bytes32 nameHash = keccak256(bytes(name));
         NameRecord storage rec = _records[nameHash];
         if (rec.owner == address(0)) revert NotRegistered(nameHash);
         if (rec.owner != msg.sender) revert NotOwner(nameHash, msg.sender);
 
-        // Remove old reverse mapping
+        bytes32 newDidHash = keccak256(bytes(newDid));
         bytes32 oldDidHash = keccak256(bytes(rec.did));
-        delete didToName[oldDidHash];
+
+        // PR #8 fix : if the new DID is already mapped to a DIFFERENT name,
+        // reject. Same-DID self-updates (newDid == oldDid) are allowed as a
+        // no-op for callers that want to refresh updatedAt.
+        if (newDidHash != oldDidHash && bytes(didToName[newDidHash]).length != 0) {
+            revert DIDAlreadyClaimed(newDidHash);
+        }
+
+        // Remove old reverse mapping (no-op if same DID)
+        if (newDidHash != oldDidHash) {
+            delete didToName[oldDidHash];
+        }
 
         rec.did = newDid;
         rec.updatedAt = block.timestamp;
 
-        // Add new reverse mapping
-        bytes32 newDidHash = keccak256(bytes(newDid));
         didToName[newDidHash] = name;
 
         emit NameUpdated(name, newDid, msg.sender, block.timestamp);