Affected Software: Babel: Multilingual Site module for CMS Made Simple
Affected Version: 0.4.1 and earlier
Patched Version: None - project is no longer under development
CVE Identifier: TBD
Vulnerability type: CWE-601: URL Redirection to Untrusted Site ('Open 
Redirect')
Severity Rating: CVSS v3 Base Score: 6.1 
(AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N)
Security Researcher: Jan Kopriva @ Alef Nula

Summary:
The Babel multi-language module for CMSMS contains an open redirection 
vulnerability in a script within the redirect.php file. The script takes 
an argument specifying a URL to which a browser should be redirected. 
This URL may be completely arbitrary. It is therefore possible to craft 
a link to a Babel-enabled site which causes redirection to any URL 
specified, even outside the originating domain. This is especially 
useful for phishing attacks, when attacker creates a link to a safe 
site, which, without the knowledge of a user, redirects him or her to a 
fake/malicious site. All CMSMS sites with Babel module installed are 
affected, since redirect.php is always publically accessible.

Detailed description:
The Babel module (http://dev.cmsmadesimple.org/projects/babel) provides 
CMSMS sites with the capacity to easily switch between multiple 
translations of web page content. Desired translation may be chosen by 
sending a GET request to vulnerable.site/modules/babel/redirect.php. 
Under normal conditions, this PHP script takes two arguments - "newlang" 
and "newurl". The first argument sets the desired language for the 
translation and the second one sets URL which should be displayed in 
selected language.
A non-working example of what the URL might look like is 
https://www.vulnerable.site/modules/babel/redirect.php?newlang=en_US&newurl=https://www.vulnerable.site/about.
The vulnerability is caused by the absence of any filtering when the 
parameter "newurl" is processed (the parametr "newlang" is - for our 
purposes - optional and may be omitted).
Further information regarding the vulnerability may be found at:
https://www.untrustednetwork.net/en/2019/02/20/open-redirection-vulnerability-in-babel/
https://www.untrustednetwork.net/en/2019/03/02/how-big-of-a-problem-is-the-open-redirect-in-babel/

Proof of Concept:
https://www.vulnerable.site/modules/babel/redirect.php?newurl=https://www.malicious.site/.

Recommendation:
Removal of the Babel module from any affected site.

Disclosure timeline:
Developer Contacted: 2. 2. 2019
Developer Responded: 11. 2. 2019 (project abandoned, no new versions are 
to be expected)
Disclosure to CSIRT network: 14. 2. 2019
Public Disclosure: 23. 2. 2019