This site is the archived OWASP Foundation Wiki and is no longer accepting Account Requests.
To view the new OWASP Foundation website, please visit https://owasp.org
Difference between revisions of "Top 10 2010-Test"
| Line 28: | Line 28: | ||
|} | |} | ||
</center> | </center> | ||
| − | <table><tr><td style="width:50%;background-color: | + | <table |
| + | style="border: none; text-align: left; width: 100%; border-spacing:5px 5px;"> | ||
| + | <tbody> | ||
| + | <tr> | ||
| + | <td style="vertical-align: top; width: 50%; border: 2px solid rgb(79, 129, 189);background-color: rgb(242, 242, 242);"> | ||
{{Top_10_2010:SubsectionVulnerableTemplate|XSS| | {{Top_10_2010:SubsectionVulnerableTemplate|XSS| | ||
You need to ensure that all user supplied input sent back to the browser is verified to be safe (via input validation), and that user input is properly escaped before it is included in the output page. Proper output encoding ensures that such input is always treated as text in the browser, rather than active content that might get executed. | You need to ensure that all user supplied input sent back to the browser is verified to be safe (via input validation), and that user input is properly escaped before it is included in the output page. Proper output encoding ensures that such input is always treated as text in the browser, rather than active content that might get executed. | ||
| Line 35: | Line 39: | ||
Web 2.0 technologies, such as AJAX, make XSS much more difficult to detect via automated tools. | Web 2.0 technologies, such as AJAX, make XSS much more difficult to detect via automated tools. | ||
| − | }}</td><td style="width:50%;> | + | }}</td> |
| + | <td style="vertical-align: top; width: 50%; border: 2px solid rgb(79, 129, 189);background-color: rgb(242, 242, 242);"> | ||
{{Top_10_2010:SubsectionPreventionTemplate|XSS| | {{Top_10_2010:SubsectionPreventionTemplate|XSS| | ||
Preventing XSS requires keeping untrusted data separate from active browser content. | Preventing XSS requires keeping untrusted data separate from active browser content. | ||
# The preferred option is to properly escape all untrusted data based on the HTML context (body, attribute, JavaScript, CSS, or URL) that the data will be placed into. Developers need to include this escaping in their applications unless their UI framework does this for them. See the [[XSS_(Cross_Site_Scripting)_Prevention_Cheat_Sheet | OWASP XSS Prevention Cheat Sheet]] for more information about data escaping techniques. | # The preferred option is to properly escape all untrusted data based on the HTML context (body, attribute, JavaScript, CSS, or URL) that the data will be placed into. Developers need to include this escaping in their applications unless their UI framework does this for them. See the [[XSS_(Cross_Site_Scripting)_Prevention_Cheat_Sheet | OWASP XSS Prevention Cheat Sheet]] for more information about data escaping techniques. | ||
# Positive or “whitelist” input validation with appropriate canonicalization and decoding is also recommended as it helps protect against XSS, but is <u>not a complete defense</u> as many applications require special characters in their input. Such validation should, as much as possible, decode any encoded input, and then validate the length, characters, format, and any business rules on that data before accepting the input. | # Positive or “whitelist” input validation with appropriate canonicalization and decoding is also recommended as it helps protect against XSS, but is <u>not a complete defense</u> as many applications require special characters in their input. Such validation should, as much as possible, decode any encoded input, and then validate the length, characters, format, and any business rules on that data before accepting the input. | ||
| − | }}</td></tr><tr><td> | + | }}</td></tr><tr> |
| + | <td style="vertical-align: top; width: 50%; border: 2px solid rgb(79, 129, 189);background-color: rgb(242, 242, 242);"> | ||
{{Top_10_2010:SubsectionExampleTemplate|XSS|}} | {{Top_10_2010:SubsectionExampleTemplate|XSS|}} | ||
The application uses untrusted data in the construction of the following HTML snippet without validation or escaping: | The application uses untrusted data in the construction of the following HTML snippet without validation or escaping: | ||
| Line 49: | Line 55: | ||
Note that attackers can also use XSS to defeat any automated CSRF defense the application might employ. See [[Top_10_2010-A5 | A5 for info on CSRF]]. | Note that attackers can also use XSS to defeat any automated CSRF defense the application might employ. See [[Top_10_2010-A5 | A5 for info on CSRF]]. | ||
| − | </td><td> | + | </td> |
| + | <td style="vertical-align: top; width: 50%; border: 2px solid rgb(79, 129, 189);background-color: rgb(242, 242, 242);"> | ||
{{Top_10_2010:SubsectionReferencesTemplate|XSS}} | {{Top_10_2010:SubsectionReferencesTemplate|XSS}} | ||
{{Top_10_2010:SubSubsectionOWASPReferencesTemplate}} | {{Top_10_2010:SubSubsectionOWASPReferencesTemplate}} | ||
Revision as of 02:28, 26 April 2010
NOTE: THIS IS NOT THE LATEST VERSION. Please visit the OWASP Top 10 project page to find the latest edition.
| Threat Agents | Attack Vectors | Security Weakness | Technical Impacts | Business Impacts | |
|---|---|---|---|---|---|
| ______ | Exploitability AVERAGE |
Prevalence VERY WIDESPREAD |
Detectability EASY |
Impact MODERATE |
______ |
| Consider anyone who can send untrusted data to the system, including external users, internal users, and administrators. | Attacker sends text- based attack scripts that exploit the interpreter in the browser. Almost any source of data can be an attack vector, including internal sources such as data from the database. | XSS is the most prevalent web application security flaw. XSS flaws occur when an application includes user supplied data in a page sent to the browser without properly validating or escaping that content. There are three known types of XSS flaws: 1) Stored, 2) Reflected, and 3) DOM based XSS.
Detection of most XSS flaws is fairly easy via testing or code analysis. |
Attackers can execute scripts in a victim’s browser to hijack user sessions, deface web sites, insert hostile content, redirect users, hijack the user’s browser using malware, etc. | Consider the business value of the affected system and all the data it processes.
Also consider the business impact of public exposure of the vulnerability. | |
Am I Vulnerable to XSS?You need to ensure that all user supplied input sent back to the browser is verified to be safe (via input validation), and that user input is properly escaped before it is included in the output page. Proper output encoding ensures that such input is always treated as text in the browser, rather than active content that might get executed. Both static and dynamic tools can find some XSS problems automatically. However, each application builds output pages differently and uses different browser side interpreters such as JavaScript, ActiveX, Flash, and Silverlight, which makes automated detection difficult. Therefore, complete coverage requires a combination of manual code review and manual penetration testing, in addition to any automated approaches in use. Web 2.0 technologies, such as AJAX, make XSS much more difficult to detect via automated tools. |
How Do I Prevent XSS?Preventing XSS requires keeping untrusted data separate from active browser content.
|
Example Attack ScenariosThe application uses untrusted data in the construction of the following HTML snippet without validation or escaping: The attacker modifies the ‘CC’ parameter in their browser to: This causes the victim’s session ID to be sent to the attacker’s website, allowing the attacker to hijack the user’s current session. Note that attackers can also use XSS to defeat any automated CSRF defense the application might employ. See A5 for info on CSRF. |
ReferencesOWASP
External  |
