URL Redirection to Untrusted Site ('Open Redirect') in Products.isurlinportal

Impact

Various parts of Plone use the 'is url in portal' check for security, mostly to see if it is safe to redirect to a url. A url like https://example.org is not in the portal.
But the url https:example.org without slashes tricks our code and it is considered to be in the portal.
When redirecting, some browsers go to https://example.org, others give an error.
Attackers may use this to redirect you to their site, especially as part of a phishing attack.

Patches

The problem has been patched in Products.isurlinportal 1.2.0.
This is a recommended upgrade for all users of Plone 4.3 and 5, on Python 2.7 or higher.
It has not been tested on earlier Plone or Python versions.
Upcoming Plone 5.2.5 and higher will include the new version.

Discovered

This vulnerability was discovered and reported by Yuji Tounai of Mitsui Bussan Secure Directions, Inc. Thank you!

For more information

If you have any questions or comments about this advisory:
* Email the Plone Security Team at [email protected], especially when you think you have discovered a security problem or when you are not sure.
* Open an issue in the tracker if your question or comment can be public.