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Description
The software does not neutralize or incorrectly neutralizes “javascript:” or other URIs from dangerous attributes within tags, such as onmouseover, onload, onerror, or style.
Modes of Introduction:
– Implementation
Likelihood of Exploit:
Related Weaknesses
CWE-79
Consequences
Confidentiality, Integrity, Availability: Read Application Data, Execute Unauthorized Code or Commands
Potential Mitigations
Phase: Implementation
Effectiveness:
Description:
Carefully check each input parameter against a rigorous positive specification (allowlist) defining the specific characters and format allowed. All input should be neutralized, 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.
Phase: Implementation
Effectiveness:
Description:
Phase: Implementation
Effectiveness:
Description:
With Struts, write all data from form beans with the bean’s filter attribute set to true.
Phase: Implementation
Effectiveness: Defense in Depth
Description:
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 more recent versions of Internet Explorer and Firefox), this attribute can prevent the user’s session cookie from being accessible to malicious client-side scripts that use document.cookie. This is not a complete solution, since HttpOnly is not supported by all browsers. More importantly, XMLHTTPRequest and other powerful browser technologies provide read access to HTTP headers, including the Set-Cookie header in which the HttpOnly flag is set.
CVE References
- CVE-2001-0520
- Bypass filtering of SCRIPT tags using onload in BODY, href in A, BUTTON, INPUT, and others.
- CVE-2002-1495
- XSS in web-based email product via onmouseover event.
- CVE-2004-1935
- Onload, onmouseover, and other events in an e-mail attachment.
- CVE-2005-0945
- Onmouseover and onload events in img, link, and mail tags.
- CVE-2003-1136
- Javascript in onmouseover attribute in e-mail address or URL.
