Description
The product does not neutralize or incorrectly neutralizes "javascript:" or other URIs from dangerous attributes within tags, such as onmouseover, onload, onerror, or style.
Potential Impact
Confidentiality, Integrity, Availability
Read Application Data, Execute Unauthorized Code or Commands
Mitigations & Prevention
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
Use and specify an output encoding that can be handled by the downstream component that is reading the output. Common encodings include ISO-8859-1, UTF-7, and UTF-8. When an encoding is not specified, a downstream component may choose a different encoding, either by assuming a default encoding or automatically inferring which encoding is being used, which can be erroneous. When the encodings are inconsistent, the downstream component might treat some character or byte sequences as special, even
With Struts, write all data from form beans with the bean's filter attribute set to true.
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 technologi
Detection Methods
- Automated Static Analysis High — Automated static analysis, commonly referred to as Static Application Security Testing (SAST), can find some instances of this weakness by analyzing source code (or binary/compiled code) without having to execute it. Typically, this is done by building a model of data flow and control flow, then sea
Real-World CVE Examples
| CVE ID | Description |
|---|---|
| CVE-2001-0520 | Bypass filtering of SCRIPT tags using onload in BODY, href in A, BUTTON, INPUT, and others. |
| CVE-2002-1493 | guestbook XSS in STYLE or IMG SRC attributes. |
| CVE-2002-1965 | Javascript in onerror attribute of IMG tag. |
| CVE-2002-1495 | XSS in web-based email product via onmouseover event. |
| CVE-2002-1681 | XSS via script in <P> tag. |
| 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. |
Related Weaknesses
Taxonomy Mappings
- PLOVER: — XSS using Script in Attributes
- Software Fault Patterns: SFP24 — Tainted input to command
Frequently Asked Questions
What is CWE-83?
CWE-83 (Improper Neutralization of Script in Attributes in a Web Page) is a software weakness identified by MITRE's Common Weakness Enumeration. It is classified as a Variant-level weakness. The product does not neutralize or incorrectly neutralizes "javascript:" or other URIs from dangerous attributes within tags, such as onmouseover, onload, onerror, or style.
How can CWE-83 be exploited?
Attackers can exploit CWE-83 (Improper Neutralization of Script in Attributes in a Web Page) to read application data, execute unauthorized code or commands. This weakness is typically introduced during the Implementation phase of software development.
How do I prevent CWE-83?
Key mitigations include: 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 tha
What is the severity of CWE-83?
CWE-83 is classified as a Variant-level weakness (Low-Medium abstraction). It has been observed in 8 real-world CVEs.