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Status: Draft Weakness ID: 83 (Weakness Variant)Description Summary The software does not filter "javascript:" or other URI's from dangerous attributes within tags, such as onmouseover, onload, onerror, or style. Weakness Ordinalities Primary (where the weakness exists independent of other weaknesses) Causal Nature Explicit (an explicit
weakness resulting from behavior of the developer) Potential Mitigations Carefully check each input parameter against a rigorous positive specification (white list) defining the specific characters and format allowed. All input should be sanitized, not just parameters that the user is supposed to specify, but all data in the request, including tag attributes, hidden fields, cookies, headers, the URL itself, and so forth. A common mistake that leads to continuing XSS vulnerabilities is to validate only fields that are expected to be redisplayed by the site. We often encounter data from the request that is reflected by the application server or the application that the development team did not anticipate. Also, a field that is not currently reflected may be used by a future developer. Therefore, validating ALL parts of the HTTP request is recommended. This involves "HTML Entity Encoding" all non-alphanumeric characters from data that was received from the user and is now being written to the request. With Struts, you should write all data from form beans with the bean's filter attribute set to true. Additionally, to help mitigate XSS attacks against the user's session cookie, set the session cookie to be HttpOnly. In browsers that support the HttpOnly feature (such as Internet Explorer), this attribute prevents the user's session cookie from being accessed by client-side scripts, including scripts inserted due to a XSS attack. Observed Examples
Relationships
Taxonomy Mappings
Applicable Platforms Languages All Time of Introduction ImplementationRelated Attack Patterns
Content History Submissions PLOVER. (Externally Mined) Modifications Eric Dalci. Cigital. 2008-07-01. (External) updated Time_of_Introduction CWE Content Team. MITRE. 2008-09-08. (Internal) updated Relationships, Observed_Example, Taxonomy_Mappings, Weakness_Ordinalities Previous Entry Names XSS using Script in Attributes (changed 2008-04-11) |
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