It was found that, in certain circumstances, it was possible for a malicious web application to replace the XML parsers used by Apache Tomcat to process XSLTs for the default servlet, JSP documents, tag library descriptors (TLDs), and tag plug-in configuration files. The injected XML parser(s) could then bypass the limits imposed on XML external entities and/or gain access to the XML files processed for other web applications deployed on the same Apache Tomcat instance.