GHSA-43gx-6gv6-3jcp Products.isurlinportal has possible open redirect when using more than 2 forward slashes

• PyPI Products.isurlinportal: >= 4.0.0a1, < 4.0.0 → fixed in 4.0.0 • PyPI Products.isurlinportal: >= 3.0.0, < 3.1.0 → fixed in 3.1.0 • PyPI Products.isurlinportal: < 2.1.0 → fixed in 2.1.0 • PyPI products-isurlinportal: < 2.1.0 → fixed in 2.1.0 • PyPI products-isurlinportal: >= 3.0.0, < 3.1.0 → fixed in 3.1.0

Impact A url `/login?came_from=////evil.example` may redirect to an external website after login. Standard Plone is not affected, but if you have customised the login, for example with add-ons, you might be affected. You can try the url to check if you are affected or not. Patches The problem has been patched in `Products.isurlinportal`. • Plone 6.2: upgrade to `Products.isurlinportal` 4.0.0. • Plone 6.1: upgrade to `Products.isurlinportal` 3.1.0. • Plone 6.0: upgrade to `Products.isurlinportal` 2.1.0. • Older Plone versions don't have security support anymore. Workarounds There are no known workarounds. Background When you are anonymous and land on a page that requires a login, Plone sends you to the login form. After successful login, Plone redirects you back to the page you came from. Various other forms and pages have a similar system. This could get abused by an attacker to trick Plone into redirecting to a different website. Plone checks the page that would be redirected to. It is only accepted if it is within the Plone site domain or part of a different trusted domain. The main check for this is in the `Products.isurlinportal` package. A lot of potentially malicious urls are already safely rejected, but here a loop hole was found. This was discovered during a penetration test by the CERT-EU Team.