Summary

Type: Authorization bypass enabling owner lockout. The DELETE /workspaces/{workspace_id}/members/{user_id} endpoint is gated only by require_workspace_member(workspace_id) (default min_role="member"). Any member can remove any other member, including the workspace owner, using a single DELETE. There is no caller-role check, no target-role check, no "cannot remove last owner" guard.
File: src/praisonai-platform/praisonai_platform/api/routes/workspaces.py, lines 130-140; services/member_service.py, lines 71-78.
Root cause: MemberService.remove(workspace_id, user_id) performs the deletion without any caller-permission check or owner-protection logic. The route accepts the URL-supplied user_id and dispatches it straight through. The role hierarchy (MemberService.has_role) is implemented but never invoked here. A member-tier attacker can issue DELETE .../members/<owner_user_id> and immediately lock the legitimate owner out of the workspace.

Affected Code

File 1: src/praisonai-platform/praisonai_platform/api/routes/workspaces.py, lines 130-140.

@router.delete("/{workspace_id}/members/{user_id}", status_code=status.HTTP_204_NO_CONTENT)
async def remove_member(
    workspace_id: str,
    user_id: str,
    user: AuthIdentity = Depends(require_workspace_member),         # <-- BUG: defaults to min_role="member"
    session: AsyncSession = Depends(get_db),
):
    member_svc = MemberService(session)
    removed = await member_svc.remove(workspace_id, user_id)        # <-- removes any member, including owner
    if not removed:
        raise HTTPException(status_code=404, detail="Member not found")

File 2: src/praisonai-platform/praisonai_platform/services/member_service.py, lines 71-78.

async def remove(self, workspace_id: str, user_id: str) -> bool:
    """Remove a member from a workspace."""
    member = await self.get(workspace_id, user_id)
    if member is None:
        return False
    await self._session.delete(member)                               # <-- BUG: no caller-role check, no last-owner protection
    await self._session.flush()
    return True

Why it's wrong: member-removal is the textbook capability that must be gated on owner role. Removing the workspace owner is a permanent denial-of-service against the legitimate owner unless another owner exists. There must be (a) a caller min-role gate of "owner" or "admin", (b) a check that prevents removing a member whose role is higher than the caller's, and (c) a check that the workspace is left with at least one owner. None of these exist.

Exploit Chain

1. Attacker is a member of workspace W with role "member". State: attacker holds JWT.
2. Attacker enumerates the workspace owner's user_id via GET /workspaces/W/members (list_members has the same default-member gate, separate finding). Owner UUID O_id is now known. State: attacker holds O_id.
3. Attacker sends DELETE /workspaces/W/members/O_id with Authorization: Bearer <attacker_jwt>. State: control flow enters remove_member.
4. require_workspace_member(W, attacker) passes (attacker is a member). MemberService.remove(W, O_id) deletes the owner's member row. State: Member(workspace_id=W, user_id=O_id, role="owner") is gone.
5. Owner attempts GET /workspaces/W/... and require_workspace_member(W, O_id) returns 403. State: legitimate owner is now locked out of their own workspace.
6. Combined with the update_member_role companion advisory, the attacker first promotes themselves to owner, then removes the legitimate owner, then has uncontested control. Combined with delete_workspace, the attacker wipes the workspace after kicking the owner.
7. Final state: with one member-level token, the attacker locks the legitimate owner out of their own workspace permanently. The owner has no recourse other than database-level admin intervention.

Security Impact

Severity: sec-high. CVSS 8.1: network attack, low complexity, low privileges, no user interaction, scope unchanged, no confidentiality, high integrity (membership table corrupted), high availability (legitimate owner cannot access their own workspace).
Attacker capability: with one workspace-member token plus one DELETE request, the attacker permanently locks any other member (including the workspace owner) out of the workspace.
Preconditions: praisonai-platform is deployed multi-tenant; attacker has any membership token; owner's user_id is reachable via the (unauthenticated-for-member) list_members endpoint.
Differential: source-inspection-verified. The asymmetry between require_workspace_member's tunable min_role parameter and this endpoint's use of the default value confirms the gap. With the suggested fix below, member-tier tokens fail the gate, and removing the workspace's last owner triggers the additional guard.

Suggested Fix

--- a/src/praisonai-platform/praisonai_platform/api/routes/workspaces.py
+++ b/src/praisonai-platform/praisonai_platform/api/routes/workspaces.py
@@ -130,11 +130,21 @@
 @router.delete("/{workspace_id}/members/{user_id}", status_code=status.HTTP_204_NO_CONTENT)
 async def remove_member(
     workspace_id: str,
     user_id: str,
-    user: AuthIdentity = Depends(require_workspace_member),
+    user: AuthIdentity = Depends(_require_workspace_owner),
     session: AsyncSession = Depends(get_db),
 ):
     member_svc = MemberService(session)
+    target = await member_svc.get(workspace_id, user_id)
+    if target is not None and target.role == "owner":
+        # Refuse to remove the last owner.
+        owners = [m for m in await member_svc.list_members(workspace_id) if m.role == "owner"]
+        if len(owners) <= 1:
+            raise HTTPException(status_code=409, detail="Cannot remove the last workspace owner")
     removed = await member_svc.remove(workspace_id, user_id)
     if not removed:
         raise HTTPException(status_code=404, detail="Member not found")

The four companion workspace-mutation endpoints exhibit the same default-min-role gap and are filed as their own advisories.