diff --git a/docs/docs/30-administration/10-configuration/10-server.md b/docs/docs/30-administration/10-configuration/10-server.md
index 1f95760df..f8162cccc 100644
--- a/docs/docs/30-administration/10-configuration/10-server.md
+++ b/docs/docs/30-administration/10-configuration/10-server.md
@@ -18,7 +18,7 @@ You can also restrict the registration:
   WOODPECKER_ADMIN=john.smith,jane_doe
   ```
 
-- open registration and filtering by organizational affiliation with the setting `WOODPECKER_ORGS`
+- open registration and filtering by organizational affiliation with the setting `WOODPECKER_ORGS`. For GitLab forges group names have to exact match, so members of group `group` are not permitted access if you set `WOODPECKER_ORGS=group/subgroup`.
 
   ```ini
   WOODPECKER_OPEN=true
@@ -712,7 +712,7 @@ Example: `WOODPECKER_ADMIN=user1,user2`
 - Name: `WOODPECKER_ORGS`
 - Default: none
 
-Comma-separated list of approved organizations.
+Comma-separated list of approved organizations. For GitLab forges this is the `full_path` [attribute](https://docs.gitlab.com/api/groups/).
 
 Example: `org1,org2`
 
diff --git a/server/forge/gitlab/fixtures/groups.go b/server/forge/gitlab/fixtures/groups.go
new file mode 100644
index 000000000..c3ad6fcdd
--- /dev/null
+++ b/server/forge/gitlab/fixtures/groups.go
@@ -0,0 +1,42 @@
+// Copyright 2026 Woodpecker Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package fixtures
+
+// Two groups both named "woodpecker": the real top-level one and one an attacker
+// created below their own namespace. They are only distinguishable by full_path.
+var groupsPayload = []byte(`
+[
+	{
+		"id": 1,
+		"name": "woodpecker",
+		"path": "woodpecker",
+		"full_name": "woodpecker",
+		"full_path": "woodpecker",
+		"parent_id": null,
+		"web_url": "https://gitlab.com/groups/woodpecker",
+		"avatar_url": "https://gitlab.com/uploads/group/avatar/1/woodpecker.png"
+	},
+	{
+		"id": 2,
+		"name": "woodpecker",
+		"path": "woodpecker",
+		"full_name": "eve / woodpecker",
+		"full_path": "eve/woodpecker",
+		"parent_id": 99,
+		"web_url": "https://gitlab.com/groups/eve/woodpecker",
+		"avatar_url": "https://gitlab.com/uploads/group/avatar/2/woodpecker.png"
+	}
+]
+`)
diff --git a/server/forge/gitlab/fixtures/testdata.go b/server/forge/gitlab/fixtures/testdata.go
index c37a3bbb7..d00a892dd 100644
--- a/server/forge/gitlab/fixtures/testdata.go
+++ b/server/forge/gitlab/fixtures/testdata.go
@@ -76,6 +76,9 @@ func NewServer(t *testing.T) *httptest.Server {
 		case "/api/v4/user":
 			_, _ = w.Write(currentUserPayload)
 			return
+		case "/api/v4/groups":
+			_, _ = w.Write(groupsPayload)
+			return
 		}
 
 		// else return a 404
diff --git a/server/forge/gitlab/gitlab.go b/server/forge/gitlab/gitlab.go
index 30e127607..bb8515f23 100644
--- a/server/forge/gitlab/gitlab.go
+++ b/server/forge/gitlab/gitlab.go
@@ -203,7 +203,7 @@ func (g *GitLab) Teams(ctx context.Context, user *model.User, p *model.ListOptio
 	for i := range groups {
 		teams = append(
 			teams, &model.Team{
-				Login:  groups[i].Name,
+				Login:  groups[i].FullPath,
 				Avatar: groups[i].AvatarURL,
 			},
 		)
diff --git a/server/forge/gitlab/gitlab_test.go b/server/forge/gitlab/gitlab_test.go
index 74bcfa36f..2c4304b25 100644
--- a/server/forge/gitlab/gitlab_test.go
+++ b/server/forge/gitlab/gitlab_test.go
@@ -104,6 +104,19 @@ func Test_GitLab(t *testing.T) {
 		assert.True(t, _repo.Perm.Push)
 	})
 
+	// Test teams membership method
+	t.Run("Should identify groups by full path, not display name", func(t *testing.T) {
+		teams, err := client.Teams(ctx, &user, &model.ListOptions{Page: 1, PerPage: 10})
+		assert.NoError(t, err)
+
+		logins := make([]string, 0, len(teams))
+		for _, team := range teams {
+			logins = append(logins, team.Login)
+		}
+		// both groups are named "woodpecker", only the full path tells them apart
+		assert.Equal(t, []string{"woodpecker", "eve/woodpecker"}, logins)
+	})
+
 	// Test activate method
 	t.Run("Activate, success", func(t *testing.T) {
 		err := client.Activate(ctx, &user, &repo, "http://example.com/api/hook?access_token=token")
diff --git a/server/services/permissions/orgs_test.go b/server/services/permissions/orgs_test.go
index 0a1852387..326c315f1 100644
--- a/server/services/permissions/orgs_test.go
+++ b/server/services/permissions/orgs_test.go
@@ -32,3 +32,18 @@ func TestOrgs(t *testing.T) {
 	assert.False(t, empty.IsMember([]*model.Team{{Login: "woodpecker-ci"}}))
 	assert.False(t, empty.IsMember([]*model.Team{{Login: "not-woodpecker-ci"}}))
 }
+
+func TestOrgsRejectsSameNamedGroup(t *testing.T) {
+	org := NewOrgs([]string{"woodpecker"})
+
+	// the real top-level group
+	assert.True(t, org.IsMember([]*model.Team{{Login: "woodpecker"}}))
+
+	// anyone can create a group named "woodpecker" below their own namespace,
+	// membership there must never satisfy an allowed org of "woodpecker"
+	assert.False(t, org.IsMember([]*model.Team{{Login: "eve/woodpecker"}}))
+	assert.False(t, org.IsMember([]*model.Team{{Login: "eve/sub/woodpecker"}}))
+
+	// subgroups are not matched either, only exact membership counts
+	assert.False(t, org.IsMember([]*model.Team{{Login: "woodpecker/infra"}}))
+}