I've found a situation in which very long and nasty errors (see below for an example) can appear on the login page because of some filter / default dashboard configurations. Here are the preconditions:

1. I have a filter called "My Current Tasks" that lists all tasks assigned to a user on a given release of a specific project.

2. I have put this filter on the default dashboard as a Filter Statistic, sorted by Priority... this shows the user a nice little bar graph of how many issues are assigned to them by priority.

3. The filter is of course shared with either A) the development group or B) everyone.

EXPECTED RESULTS
The bar graph should appear on the default dashboard for any user that is logged in. If (A) above, then non-developers should not see the portlet at all, since the driving filter is not shared.

ACTUAL RESULTS
On the login page if (A) above, I see a "This portlet is no longer valid as the associated filter could not be retrieved." If (B) above, I get a very, very long Java exception on the login page that looks hideous and scares people off.

Also, if (A) above and the user logs in, developers see what is expected but non-developers see "This portlet is no longer valid as the associated filter could not be retrieved" on their dashboard. If (B) and the user logs in, it looks fine although the portlet appears with zero statistics for non-developers (of course).

RECOMMENDED SOLUTION
The dashboard (and login page!) should not try to run portlets that are driven by filters that are hidden to the current user.

EXCEPTION TRACE FROM LOGIN PAGE
This is obviously just a nasty side effect, but I've marked this as a Critical issue because this is what we get on our login page, for all to see:

n error occurred whilst rendering this message. Please contact the administrators, and inform them of this bug. Details: ------- org.apache.velocity.exception.MethodInvocationException: Invocation of method 'getAllFilterBy' in class com.atlassian.jira.web.bean.StatisticAccessorBean threw exception class java.lang.NullPointerException : null at org.apache.velocity.runtime.parser.node.ASTMethod.execute(ASTMethod.java:246) at org.apache.velocity.runtime.parser.node.ASTReference.execute(ASTReference.java:175) at org.apache.velocity.runtime.parser.node.ASTReference.value(ASTReference.java:327) at org.apache.velocity.runtime.parser.node.ASTExpression.value(ASTExpression.java:51) at org.apache.velocity.runtime.parser.node.ASTSetDirective.render(ASTSetDirective.java:95) at org.apache.velocity.runtime.parser.node.SimpleNode.render(SimpleNode.java:230) at org.apache.velocity.runtime.directive.Parse.render(Parse.java:181) at org.apache.velocity.runtime.parser.node.ASTDirective.render(ASTDirective.java:114) at org.apache.velocity.runtime.parser.node.ASTBlock.render(ASTBlock.java:55) at org.apache.velocity.runtime.parser.node.ASTIfStatement.render(ASTIfStatement.java:70) at org.apache.velocity.runtime.parser.node.SimpleNode.render(SimpleNode.java:230) at org.apache.velocity.Template.merge(Template.java:256) at org.apache.velocity.app.VelocityEngine.mergeTemplate(VelocityEngine.java:450) at com.atlassian.velocity.DefaultVelocityManager.getEncodedBody(DefaultVelocityManager.java:97) at com.atlassian.velocity.DefaultVelocityManager.getEncodedBody(DefaultVelocityManager.java:77) at com.atlassian.jira.plugin.JiraResourcedModuleDescriptor.getHtml(JiraResourcedModuleDescriptor.java:79) at com.atlassian.jira.portal.PortletImpl.getViewHtml(PortletImpl.java:47) at org.apache.jsp.dashboard_jsp._jspService(dashboard_jsp.java:1035) at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:137) at javax.servlet.http.HttpServlet.service(HttpServlet.java:853) at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:210) at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:295) at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:241) at javax.servlet.http.HttpServlet.service(HttpServlet.java:853) at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:684) at org.apache.catalina.core.ApplicationDispatcher.doForward(ApplicationDispatcher.java:432) at org.apache.catalina.core.ApplicationDispatcher.forward(ApplicationDispatcher.java:356) at com.atlassian.jira.web.dispatcher.JiraServletDispatcher.service(JiraServletDispatcher.java:260) at javax.servlet.http.HttpServlet.service(HttpServlet.java:853) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:247) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:193) at com.opensymphony.module.sitemesh.filter.PageFilter.parsePage(PageFilter.java:142) at com.opensymphony.module.sitemesh.filter.PageFilter.doFilter(PageFilter.java:58) at com.atlassian.jira.web.filters.SitemeshExcludePathFilter.doFilter(SitemeshExcludePathFilter.java:36) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:213) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:193) at com.atlassian.seraph.filter.SecurityFilter.doFilter(SecurityFilter.java:168) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:213) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:193) at com.atlassian.seraph.filter.LoginFilter.doFilter(LoginFilter.java:181) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:213) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:193) at com.atlassian.util.profiling.filters.ProfilingFilter.doFilter(ProfilingFilter.java:132) at com.atlassian.jira.web.filters.ProfilingAndErrorFilter.doFilter(ProfilingAndErrorFilter.java:25) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:213) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:193) at com.atlassian.jira.web.filters.ActionCleanupDelayFilter.doFilter(ActionCleanupDelayFilter.java:37) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:213) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:193) at com.atlassian.johnson.filters.JohnsonFilter.doFilter(JohnsonFilter.java:91) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:213) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:193) at com.atlassian.jira.web.filters.gzip.GzipFilter.doFilter(GzipFilter.java:64) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:213) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:193) at com.atlassian.core.filters.AbstractEncodingFilter.doFilter(AbstractEncodingFilter.java:36) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:213) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:193) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:256) at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:643) at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:480) at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:995) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191) at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:643) at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:480) at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:995) at org.apache.catalina.core.StandardContext.invoke(StandardContext.java:2417) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:180) at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:643) at org.apache.catalina.valves.ErrorDispatcherValve.invoke(ErrorDispatcherValve.java:171) at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:641) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:172) at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:641) at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:480) at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:995) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:174) at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:643) at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:480) at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:995) at org.apache.coyote.tomcat4.CoyoteAdapter.service(CoyoteAdapter.java:193) at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:781) at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.processConnection(Http11Protocol.java:549) at org.apache.tomcat.util.net.TcpWorkerThread.runIt(PoolTcpEndpoint.java:589) at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:666) at java.lang.Thread.run(Thread.java:534)