[WEB-8382][WEB-8383] fix(security): external-API issue comment + attachment authz (GHSA-h4p4-mwfg-qh82, GHSA-xvc5-m5jf-gvpj)

Two authorization gaps in the external API (api/views/issue.py):

- GHSA-h4p4: IssueCommentDetailAPIEndpoint uses ProjectLitePermission (any active
  project member) and edited/deleted comments by id with no author/admin check —
  a Guest could tamper with or delete anyone's comments. patch/delete now require
  the comment author OR a project admin (403 otherwise), matching the app.

- GHSA-xvc5: IssueAttachmentListCreateAPIEndpoint.get had no permission_classes
  (bare IsAuthenticated) and no membership check, while post calls
  user_has_issue_permission. Since API tokens authenticate globally, any token
  holder could list any issue's attachment metadata cross-tenant. get now enforces
  project membership on the issue, mirroring post.

Adds 6 contract tests (guest comment patch/delete 403, author/admin allowed;
outsider attachment list 403, member allowed); fail-before verified.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

apps/api/plane/api/views/issue.py

@@ -1602,6 +1602,17 @@ class IssueCommentDetailAPIEndpoint(BaseAPIView):
         Validates external ID uniqueness if provided.
         """
         issue_comment = IssueComment.objects.get(workspace__slug=slug, project_id=project_id, issue_id=issue_id, pk=pk)
+        # Only the comment author or a project admin may modify a comment.
+        # ProjectLitePermission alone lets any active member (incl. Guest) reach
+        # here, so enforce the same author/admin rule the app applies
+        # (GHSA-h4p4-mwfg-qh82).
+        if issue_comment.created_by_id != request.user.id and not ProjectMember.objects.filter(
+            project_id=project_id, member_id=request.user.id, role=ROLE.ADMIN.value, is_active=True
+        ).exists():
+            return Response(
+                {"error": "Only the comment author or a project admin can modify this comment."},
+                status=status.HTTP_403_FORBIDDEN,
+            )
         requested_data = json.dumps(self.request.data, cls=DjangoJSONEncoder)
         current_instance = json.dumps(IssueCommentSerializer(issue_comment).data, cls=DjangoJSONEncoder)
 
@@ -1671,6 +1682,15 @@ class IssueCommentDetailAPIEndpoint(BaseAPIView):
         Records deletion activity for audit purposes.
         """
         issue_comment = IssueComment.objects.get(workspace__slug=slug, project_id=project_id, issue_id=issue_id, pk=pk)
+        # Only the comment author or a project admin may delete a comment
+        # (GHSA-h4p4-mwfg-qh82).
+        if issue_comment.created_by_id != request.user.id and not ProjectMember.objects.filter(
+            project_id=project_id, member_id=request.user.id, role=ROLE.ADMIN.value, is_active=True
+        ).exists():
+            return Response(
+                {"error": "Only the comment author or a project admin can delete this comment."},
+                status=status.HTTP_403_FORBIDDEN,
+            )
         current_instance = json.dumps(IssueCommentSerializer(issue_comment).data, cls=DjangoJSONEncoder)
         issue_comment.delete()
         issue_activity.delay(
@@ -2002,6 +2022,23 @@ class IssueAttachmentListCreateAPIEndpoint(BaseAPIView):
 
         List all attachments for an issue.
         """
+        # This endpoint has no permission_classes beyond IsAuthenticated, and API
+        # tokens authenticate globally (not workspace-scoped), so enforce project
+        # membership on the issue the same way post() does — otherwise any token
+        # holder could read any issue's attachment metadata cross-tenant
+        # (GHSA-xvc5-m5jf-gvpj).
+        issue = Issue.objects.get(pk=issue_id, workspace__slug=slug, project_id=project_id)
+        if not user_has_issue_permission(
+            request.user.id,
+            project_id=project_id,
+            issue=issue,
+            allowed_roles=[ROLE.ADMIN.value, ROLE.MEMBER.value, ROLE.GUEST.value],
+            allow_creator=True,
+        ):
+            return Response(
+                {"error": "You are not allowed to view these attachments"},
+                status=status.HTTP_403_FORBIDDEN,
+            )
         # Get all the attachments
         issue_attachments = FileAsset.objects.filter(
             issue_id=issue_id,

apps/api/plane/tests/contract/api/test_external_api_issue_authz.py

@@ -0,0 +1,184 @@
+# Copyright (c) 2023-present Plane Software, Inc. and contributors
+# SPDX-License-Identifier: AGPL-3.0-only
+# See the LICENSE file for details.
+
+"""Contract tests for external-API issue comment + attachment authorization.
+
+Regression coverage for:
+
+* GHSA-h4p4-mwfg-qh82 — ``IssueCommentDetailAPIEndpoint`` (``ProjectLitePermission``,
+  any active member) edited/deleted comments by id with no author/admin check, so
+  a Guest could tamper with anyone's comments.
+* GHSA-xvc5-m5jf-gvpj — ``IssueAttachmentListCreateAPIEndpoint.get`` had no
+  ``permission_classes`` (bare ``IsAuthenticated``) and no membership check, so any
+  API-token holder could list any issue's attachment metadata cross-tenant.
+
+The fixes: comment patch/delete require the comment author or a project admin;
+the attachment GET enforces project membership on the issue (mirroring ``post``).
+"""
+
+from uuid import uuid4
+
+import pytest
+from rest_framework import status
+from rest_framework.test import APIClient
+
+from plane.db.models import (
+    APIToken,
+    FileAsset,
+    Issue,
+    IssueComment,
+    Project,
+    ProjectMember,
+    User,
+    WorkspaceMember,
+)
+
+COMMENT_URL = "/api/v1/workspaces/{slug}/projects/{project_id}/issues/{issue_id}/comments/{pk}/"
+ATTACH_URL = "/api/v1/workspaces/{slug}/projects/{project_id}/issues/{issue_id}/issue-attachments/"
+
+
+def _user(prefix):
+    unique = uuid4().hex[:8]
+    user = User.objects.create(email=f"{prefix}-{unique}@plane.so", username=f"{prefix}_{unique}")
+    user.set_password("test-password")
+    user.save()
+    return user
+
+
+def _token_client(user):
+    token = APIToken.objects.create(user=user, label=f"tok-{uuid4().hex[:6]}", token=f"tok-{uuid4().hex}")
+    client = APIClient()
+    client.credentials(HTTP_X_API_KEY=token.token)
+    return client
+
+
+@pytest.fixture
+def project(db, workspace, create_user):
+    project = Project.objects.create(
+        name="Ext API Project", identifier="EA", workspace=workspace, created_by=create_user
+    )
+    # create_user is the project ADMIN
+    ProjectMember.objects.create(project=project, member=create_user, workspace=workspace, role=20, is_active=True)
+    return project
+
+
+def _project_member(workspace, project, *, role):
+    user = _user(f"role{role}")
+    WorkspaceMember.objects.create(workspace=workspace, member=user, role=role, is_active=True)
+    ProjectMember.objects.create(project=project, member=user, workspace=workspace, role=role, is_active=True)
+    return user
+
+
+@pytest.fixture
+def issue(db, workspace, project, create_user):
+    issue = Issue(name="Issue", project=project, workspace=workspace)
+    issue.save(created_by_id=create_user.id)
+    return issue
+
+
+# --- h4p4: comment tamper -----------------------------------------------------
+
+
+@pytest.fixture
+def author(db, workspace, project):
+    return _project_member(workspace, project, role=15)
+
+
+@pytest.fixture
+def comment(db, workspace, project, issue, author):
+    c = IssueComment(
+        workspace=workspace, project=project, issue=issue, comment_html="<p>original</p>", actor=author
+    )
+    c.save(created_by_id=author.id)
+    return c
+
+
+@pytest.mark.contract
+@pytest.mark.django_db
+class TestExternalApiCommentAuthz:
+    """A Guest / non-author must not edit or delete another user's comment."""
+
+    def test_guest_cannot_patch_comment(self, workspace, project, issue, comment):
+        guest = _project_member(workspace, project, role=5)
+        response = _token_client(guest).patch(
+            COMMENT_URL.format(slug=workspace.slug, project_id=project.id, issue_id=issue.id, pk=comment.id),
+            {"comment_html": "<p>tampered</p>"},
+            format="json",
+        )
+        assert response.status_code == status.HTTP_403_FORBIDDEN, (
+            f"Got {response.status_code}: {getattr(response, 'data', None)!r}"
+        )
+        comment.refresh_from_db()
+        assert comment.comment_html == "<p>original</p>"
+
+    def test_guest_cannot_delete_comment(self, workspace, project, issue, comment):
+        guest = _project_member(workspace, project, role=5)
+        response = _token_client(guest).delete(
+            COMMENT_URL.format(slug=workspace.slug, project_id=project.id, issue_id=issue.id, pk=comment.id)
+        )
+        assert response.status_code == status.HTTP_403_FORBIDDEN, (
+            f"Got {response.status_code}: {getattr(response, 'data', None)!r}"
+        )
+        assert IssueComment.objects.filter(pk=comment.id).exists()
+
+    def test_author_can_patch_own_comment(self, workspace, project, issue, comment, author):
+        response = _token_client(author).patch(
+            COMMENT_URL.format(slug=workspace.slug, project_id=project.id, issue_id=issue.id, pk=comment.id),
+            {"comment_html": "<p>edited by author</p>"},
+            format="json",
+        )
+        assert response.status_code == status.HTTP_200_OK, (
+            f"Got {response.status_code}: {getattr(response, 'data', None)!r}"
+        )
+
+    def test_admin_can_delete_comment(self, workspace, project, issue, comment, create_user):
+        """Positive control: a project admin may delete another user's comment."""
+        response = _token_client(create_user).delete(
+            COMMENT_URL.format(slug=workspace.slug, project_id=project.id, issue_id=issue.id, pk=comment.id)
+        )
+        assert response.status_code == status.HTTP_204_NO_CONTENT, (
+            f"Got {response.status_code}: {getattr(response, 'data', None)!r}"
+        )
+
+
+# --- xvc5: attachment metadata disclosure -------------------------------------
+
+
+@pytest.fixture
+def attachment(db, workspace, project, issue):
+    return FileAsset.objects.create(
+        attributes={"name": "secret.pdf", "type": "application/pdf", "size": 100},
+        asset=f"{workspace.id}/{uuid4().hex}-secret.pdf",
+        size=100,
+        workspace=workspace,
+        project=project,
+        issue_id=issue.id,
+        entity_type=FileAsset.EntityTypeContext.ISSUE_ATTACHMENT,
+        is_uploaded=True,
+    )
+
+
+@pytest.mark.contract
+@pytest.mark.django_db
+class TestExternalApiAttachmentAuthz:
+    """A token holder with no project membership must not read attachment metadata."""
+
+    def test_outsider_cannot_list_attachments(self, workspace, project, issue, attachment):
+        outsider = _user("outsider")  # valid token, NO membership anywhere
+        response = _token_client(outsider).get(
+            ATTACH_URL.format(slug=workspace.slug, project_id=project.id, issue_id=issue.id)
+        )
+        assert response.status_code == status.HTTP_403_FORBIDDEN, (
+            f"Got {response.status_code}: {getattr(response, 'data', None)!r}"
+        )
+
+    def test_project_member_can_list_attachments(self, workspace, project, issue, attachment):
+        member = _project_member(workspace, project, role=15)
+        response = _token_client(member).get(
+            ATTACH_URL.format(slug=workspace.slug, project_id=project.id, issue_id=issue.id)
+        )
+        assert response.status_code == status.HTTP_200_OK, (
+            f"Got {response.status_code}: {getattr(response, 'data', None)!r}"
+        )
+        assert len(response.data) == 1