XSS (Cross-site Scripting) allows an attacker to execute a dynamic script (Javascript, VbScript) in the context of the application. This allows several different attack opportunities, mostly hijacking the current session of the user or changing the look of the page by changing the HTML on the fly to steal the user's credentials. This happens because the input entered by a user has been interpreted as HTML/Javascript/VbScript by the browser.
XSS targets the users of the application instead of the server. Although this is a limitation, since it allows attackers to hijack other users' session, an attacker might attack an administrator to gain full control over the application.
Impact
There are many different attacks that can be leveraged through the use of XSS, including:
Hi-jacking users' active session
Changing the look of the page within the victims browser.
Mounting a successful phishing attack.
Intercept data and perform man-in-the-middle attacks.
Remedy
The issue occurs because the browser interprets the input as active HTML, Javascript or VbScript. To avoid this, all input and output from the application should be filtered. Output should be filtered according to the output format and location. Typically the output location is HTML. Where the output is HTML ensure that all active content is removed prior to its presentation to the server.
Prior to sanitizing user input, ensure you have a pre-defined list of both expected and acceptable characters with which you populate a white-list. This list needs only be defined once and should be used to sanitize and validate all subsequent input.
There are a number of pre-defined, well structured white-list libraries available for many different environments, good examples of these include, OWASP Reform and Microsoft Anti Cross-site Scripting libraries are good examples.
HTTP/1.1 500 Internal Server Error Server: Apache-Coyote/1.1 Content-Type: text/html;charset=ISO-8859-1 Content-Encoding: Vary: Accept-Encoding Date: Tue, 03 May 2011 13:50:08 GMT Connection: close
<!-- An Aggregate Knowledge internal error occurred; Unable to service request. java.lang.IllegalArgumentException: Could not convert "'"--></style></script><script>netsparker(0x000014)</script>" to int / long. at net.agkn.module.common.parameter.ParameterDefinition.castSingleValue(ParameterDefinition.java:259) at net.agkn.module.common.parameter.ParameterDefinition.castValue(ParameterDefinition.java:209) at net.agkn.module.common.parameter.ParameterCollection.setParameterValue(ParameterCollection.java:108) at net.agkn.module.common.impl.ModuleRequest.setParameterValue(ModuleRequest.java:162) at net.agkn.html.controller.behavior.IFrameController.processBehaviorCollection(IFrameController.java:366) at net.agkn.html.controller.behavior.IFrameController.handleRequest(IFrameController.java:313) at org.springframework.web.servlet.mvc.SimpleControllerHandlerAdapter.handle(SimpleControllerHandlerAdapter.java:48) at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:875) at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:807) at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:571) at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:501) at javax.servlet.http.HttpServlet.service(HttpServlet.java:627) at javax.servlet.http.HttpServlet.service(HttpServlet.java:729) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:269) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:188) at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:679) at org.apache.catalina.core.ApplicationDispatcher.processRequest(ApplicationDispatcher.java:461) at org.apache.catalina.core.ApplicationDispatcher.doForward(ApplicationDispatcher.java:399) at org.apache.catalina.core.ApplicationDispatcher.forward(ApplicationDispatcher.java:301) at org.tuckey.web.filters.urlrewrite.NormalRewrittenUrl.doRewrite(NormalRewrittenUrl.java:195) at org.tuckey.web.filters.urlrewrite.RuleChain.handleRewrite(RuleChain.java:159) at org.tuckey.web.filters.urlrewrite.RuleChain.doRules(RuleChain.java:141) at org.tuckey.web.filters.urlrewrite.UrlRewriter.processRequest(UrlRewriter.java:90) at org.tuckey.web.filters.urlrewrite.UrlRewriteFilter.doFilter(UrlRewriteFilter.java:417) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:215) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:188) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:213) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:172) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:117) at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:581) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:108) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:174) at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:873) at org.apache.coyote.http11.Http11BaseProtocol$Http11ConnectionHandler.processConnection(Http11BaseProtocol.java:665) at org.apache.tomcat.util.net.PoolTcpEndpoint.processSocket(PoolTcpEndpoint.java:528) at org.apache.tomcat.util.net.LeaderFollowerWorkerThread.runIt(LeaderFollowerWorkerThread.java:81) at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:689) at java.lang.Thread.run(Thread.java:735)-->
The Server responded with an HTTP status 500. This indicates that there is a server-side error. Reasons may vary. The behavior should be analysed carefully. If Netsparker is able to find a security issue in the same resource it will report this as a separate vulnerability.
Impact
The impact may vary depending on the condition. Generally this indicates poor coding practices, not enough error checking, sanitization and whitelisting. However there might be a bigger issue such as SQL Injection. If that's the case Netsparker will check for other possible issues and report them separately.
Remedy
Analyse this issue and review the application code in order to handle unexpected errors, this should be a generic practice which does not disclose further information upon an error. All errors should be handled server side only.
HTTP/1.1 500 Internal Server Error Server: Apache-Coyote/1.1 Content-Type: text/html;charset=ISO-8859-1 Content-Encoding: Vary: Accept-Encoding Date: Tue, 03 May 2011 13:50:08 GMT Connection: close
<!-- An Aggregate Knowledge internal error occurred; Unable to service request. java.lang.IllegalArgumentException: Could not convert "';WAITFOR DELAY '0:0:25'--" to int / long. at net.agkn.module.common.parameter.ParameterDefinition.castSingleValue(ParameterDefinition.java:259) at net.agkn.module.common.parameter.ParameterDefinition.castValue(ParameterDefinition.java:209) at net.agkn.module.common.parameter.ParameterCollection.setParameterValue(ParameterCollection.java:108) at net.agkn.module.common.impl.ModuleRequest.setParameterValue(ModuleRequest.java:162) at net.agkn.html.controller.behavior.IFrameController.processBehaviorCollection(IFrameController.java:366) at net.agkn.html.controller.behavior.IFrameController.handleRequest(IFrameController.java:313) at org.springframework.web.servlet.mvc.SimpleControllerHandlerAdapter.handle(SimpleControllerHandlerAdapter.java:48) at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:875) at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:807) at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:571) at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:501) at javax.servlet.http.HttpServlet.service(HttpServlet.java:627) at javax.servlet.http.HttpServlet.service(HttpServlet.java:729) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:269) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:188) at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:679) at org.apache.catalina.core.ApplicationDispatcher.processRequest(ApplicationDispatcher.java:461) at org.apache.catalina.core.ApplicationDispatcher.doForward(ApplicationDispatcher.java:399) at org.apache.catalina.core.ApplicationDispatcher.forward(ApplicationDispatcher.java:301) at org.tuckey.web.filters.urlrewrite.NormalRewrittenUrl.doRewrite(NormalRewrittenUrl.java:195) at org.tuckey.web.filters.urlrewrite.RuleChain.handleRewrite(RuleChain.java:159) at org.tuckey.web.filters.urlrewrite.RuleChain.doRules(RuleChain.java:141) at org.tuckey.web.filters.urlrewrite.UrlRewriter.processRequest(UrlRewriter.java:90) at org.tuckey.web.filters.urlrewrite.UrlRewriteFilter.doFilter(UrlRewriteFilter.java:417) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:215) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:188) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:213) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:172) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:117) at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:581) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:108) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:174) at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:873) at org.apache.coyote.http11.Http11BaseProtocol$Http11ConnectionHandler.processConnection(Http11BaseProtocol.java:665) at org.apache.tomcat.util.net.PoolTcpEndpoint.processSocket(PoolTcpEndpoint.java:528) at org.apache.tomcat.util.net.LeaderFollowerWorkerThread.runIt(LeaderFollowerWorkerThread.java:81) at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:689) at java.lang.Thread.run(Thread.java:735)-->
Cookie was not marked as HTTPOnly. HTTPOnly cookies can not be read by client-side scripts therefore marking a cookie as HTTPOnly can provide an additional layer of protection against Cross-site Scripting attacks..
Impact
During a Cross-site Scripting attack an attacker might easily access cookies and hijack the victim's session.
Actions to Take
See the remedy for solution
Consider marking all of the cookies used by the application as HTTPOnly (After these changes javascript code will not able to read cookies.
Remedy
Mark the cookie as HTTPOnly. This will be an extra layer of defence against XSS. However this is not a silver bullet and will not protect the system against Cross-site Scripting attacks. An attacker can use a tool such as XSS Tunnel to bypass HTTPOnly protection.
Netsparker identified that the target web server is disclosing Apache Coyote version in the HTTP response. This information can help an attacker to gain a greater understanding of the systems in use and potentially develop further attacks targeted at the specific version of Apache.
Impact
An attacker can look for specific security vulnerabilities for the version identified in the SERVER header. The attacker can also use this information in conjunction with the other vulnerabilities in the application or the web server.
Remedy
Configure your web server to prevent information leakage from the SERVER header of its HTTP response.
