Description
The product receives input from an upstream component, but it does not neutralize or incorrectly neutralizes special characters such as "<", ">", and "&" that could be interpreted as web-scripting elements when they are sent to a downstream component that processes web pages.
Potential Impact
Confidentiality, Integrity, Availability
Read Application Data, Execute Unauthorized Code or Commands
Demonstrative Examples
<% for (Iterator i = guestbook.iterator(); i.hasNext(); ) {Entry e = (Entry) i.next(); %><p>Entry #<%= e.getId() %></p><p><%= e.getText() %></p><%} %>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 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 f
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-2002-0938 | XSS in parameter in a link. |
| CVE-2002-1495 | XSS in web-based email product via attachment filenames. |
| CVE-2003-1136 | HTML injection in posted message. |
| CVE-2004-2171 | XSS not quoted in error page. |
Related Weaknesses
Taxonomy Mappings
- PLOVER: — Basic XSS
- Software Fault Patterns: SFP24 — Tainted input to command
Frequently Asked Questions
What is CWE-80?
CWE-80 (Improper Neutralization of Script-Related HTML Tags in a Web Page (Basic XSS)) is a software weakness identified by MITRE's Common Weakness Enumeration. It is classified as a Variant-level weakness. The product receives input from an upstream component, but it does not neutralize or incorrectly neutralizes special characters such as "<", ">", and "&" that could be interpreted as web-scripting ele...
How can CWE-80 be exploited?
Attackers can exploit CWE-80 (Improper Neutralization of Script-Related HTML Tags in a Web Page (Basic XSS)) 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-80?
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-80?
CWE-80 is classified as a Variant-level weakness (Low-Medium abstraction). It has been observed in 4 real-world CVEs.