Common Attack Pattern Enumeration and Classification
A Community Resource for Identifying and Understanding Attacks
An attacker makes use of Cascading Style Sheets (CSS) injection to steal data cross domain from the victim's browser. The attack works by abusing the standards relating to loading of CSS: 1. Send cookies on any load of CSS (including cross-domain) 2. When parsing returned CSS ignore all data that does not make sense before a valid CSS descriptor is found by the CSS parser By having control of some text in the victim's domain, the attacker is able to inject a seemingly valid CSS string. It does not matter if this CSS string is preceded by other data. The CSS parser will still locate the CSS string. If the attacker is able to control two injection points, one before the cross domain data that the attacker is interested in receiving and the other one after, the attacker can use this attack to steal all of the data in between these two CSS injection points when referencing the injected CSS while performing rendering on the site that the attacker controls. When rendering, the CSS parser will detect the valid CSS string to parse and ignore the data that "does not make sense". That data will simply be rendered. That data is in fact the data that the attacker just stole cross domain. The stolen data may contain sensitive information, such CSRF protection tokens.
The table below shows the other attack patterns and high level categories that are related to this attack pattern. These relationships are defined as ChildOf and ParentOf, and give insight to similar items that may exist at higher and lower levels of abstraction. In addition, relationships such as CanFollow, PeerOf, and CanAlsoBe are defined to show similar attack patterns that the user may want to explore.
The table below shows the views that this attack pattern belongs to and top level categories within that view.
Attacker controlled site/page to render a page referencing the injected CSS string
A Related Weakness relationship associates a weakness with this attack pattern. Each association implies a weakness that must exist for a given attack to be successful. If multiple weaknesses are associated with the attack pattern, then any of the weaknesses (but not necessarily all) may be present for the attack to be successful. Each related weakness is identified by a CWE identifier.
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