GHSA-6x92-6vx4-5fwr

## Impact

The only authorization gate on the duplicate flow is `PageAdmin.has_add_permission`, which checks `user_can_add_page(user, site)` / `user_can_add_subpage(...)` — i.e. *“may this user create a page at all”*. Nothing checks the user’s relationship to the page being copied:

- `cms/admin/forms.py` — `DuplicatePageForm.source = ModelChoiceField(queryset=Page.objects.all(), widget=HiddenInput())` spans **every page in the database, on every site**. - `cms/admin/forms.py` — `AddPageForm.__init__` returns early when the `source` widget is hidden, so the queryset is **never narrowed** to the user’s site/subtree. - `cms/admin/forms.py` — `AddPageForm.clean()` validates only URL uniqueness; `source` is never validated against the user. - `cms/admin/pageadmin.py` — `duplicate()` seeds `source` from the URL **only on GET**; on POST the value comes entirely from the request body. - `cms/admin/forms.py` — `AddPageForm.save()` → `from_source()` performs `source.copy(..., permissions=False)` and copies **every placeholder and all plugins** of `source` into a new page on the attacker’s site. Because `permissions=False` drops the source’s view restrictions, the resulting copy is fully readable by the attacker.

This crosses a real privilege boundary: a staff user restricted (via `CMS_PERMISSION`) to their own site or subtree can exfiltrate the content of restricted pages and of pages belonging to other tenants.

**Read-back is trivial (verified):** the copy is created on the attacker’s site and, because `copy(..., permissions=False)` strips the source’s view restrictions, the new page is *unrestricted*. `user_can_view_page()` then returns `True` for it (unrestricted + `PUBLIC_FOR`), so the attacker — or even an anonymous visitor — can read the duplicated content directly from the front end. No further permission on the new page is required.

## Proof of concept

1. Log in as a staff user `attacker` who has *add page* permission but **no** view/change permission on a target (secret / other-site) page `SECRET_ID`. 2. Send (the URL `<id>` only needs to be a `PageContent` the attacker can already see — e.g. one of their own pages; the victim id goes in the POST body):

```http POST /admin/cms/pagecontent/<MY_OWN_PAGECONTENT_ID>/duplicate/ HTTP/1.1 Cookie: sessionid=<attacker session> Content-Type: application/x-www-form-urlencoded

csrfmiddlewaretoken=...&title=x&slug=x&language=en&source=<SECRET_ID> ```

3. A new, unrestricted page is created under the attacker’s site containing a verbatim copy of the secret page’s plugins, which the attacker can now preview/edit/read.

## Patches

Enforce an object-level permission check on `source`:

```python class DuplicatePageForm(AddPageForm): source = forms.ModelChoiceField( queryset=Page.objects.all(), required=True, widget=forms.HiddenInput(), )

def clean_source(self): source = self.cleaned_data.get("source") if source and not user_can_view_page(self._user, source): raise ValidationError(_("You do not have permission to copy this page.")) return source ```

(`user_can_view_page` is imported from `cms.utils.page_permissions`.)

## Workarounds

Until patched, restrict access to the `cms.add_page` permission to fully-trusted staff, or disable the duplicate action for delegated/limited editors.

## References

- `cms/admin/pageadmin.py` — `duplicate()`, `has_add_permission()`, `get_urls()` - `cms/admin/forms.py` — `DuplicatePageForm`, `AddPageForm.__init__/clean/save/from_source` - Regression tests: `cms/tests/test_forms.py::DuplicatePageFormSecurityTestCase`