Original release date: February 4, 2014
Last revised: February 4, 2014
Discovered by: Vicente Aguilera Diaz
Severity: 4.3/10 (CVSSv2 Base Scored)
Boxcryptor is an easy-to-use encryption software optimized for the cloud. It allows the secure se of cloud storage services without sacrificing comfort.
Boxcryptor supports all major cloud storage providers (such as Dropbox, Google Drive, Microsoft SkyDrive, SugarSync) and supports all the clouds that use the WebDAV standard (such as Cubby, Strato HiDrive, and ownCloud).
Has been detected a XSS vulnerability in www.boxcryptor.com. Cross-Site Scripting attacks are a type of injection problem, in which malicious scripts are injected into the otherwise benign and trusted web sites.
Cross-site scripting (XSS) attacks occur when an attacker uses a web application to send malicious code, generally in the form of a browser side script, to a different end user. Flaws that allow these attacks to succeed are quite widespread and occur anywhere a web application uses input from a user in the output it generates without validating or encoding it.
An attacker can use XSS to send a malicious script to an unsuspecting user. The end user’s browser has no way to know that the script should not be trusted, and will execute the script. Because it thinks the script came from a trusted source, the malicious script can access any cookies, session tokens, or other sensitive information retained by your browser and used with that site.
These scripts can even rewrite the content of the HTML page.
PROOF OF CONCEPT
Next, we show a typical request to save changes in "My Account" option: POST /app/user/modify/<userid> HTTP/1.1 Host: www.boxcryptor.com ... firstname=<firstname>&lastname=<lastname>&username=<email>&_newsletter= where: - is a numeric user ID generated by boxcryptor - is the firstname specified by the user - is the lastname specified by the user - is the email address specified by the user A malicious user can inject arbitrary HTML/script code in the <email> parameter. For example: POST /app/user/modify/3805739018726483071 HTTP/1.1 Host: www.boxcryptor.com ... firstname=John&lastname=Smithemail@example.com<h1> </h1><center>This+is+a+XSS+example</center>&_newsletter= </email></email></lastname></firstname></userid></email></lastname></firstname></userid>
An attacker can execute arbitrary HTML or script code in a targeted user's browser. This can leverage to steal sensitive information as user credentials, personal data, etc.
This vulnerability has been discovered by Vicente Aguilera Diaz vaguilera (at) isecauditors (dot) com).
February 4, 2014: Initial release
February 4, 2014: Discovered by Internet Security Auditors
February 6, 2014: Contact with the developer team
February 10, 2014: Confirmed by vendor
February 10, 2014: Vendor deployed a new version
February 13, 2014: Internet Security Auditors release the advisory
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