After further investigating this issue, this was caused by the reverse proxy that I set up in front of FusionAuth.

@dan I am using caprover as PaaS, and it has NGINX fully integrated. It's only happening on their latest version. I already raised an issue with them (https://github.com/caprover/caprover/issues/1035).

I tried to reconfigure their proxy manually but couldn't get it to work. I just rolled it back to their earlier version.

@dan I am using caprover as PaaS, and it has NGINX fully integrated. It's only happening on their latest version. I already raised an issue with them (https://github.com/caprover/caprover/issues/1035).

I tried to reconfigure their proxy manually but couldn't get it to work. I just rolled it back to their earlier version.

After further investigating this issue, this was caused by the reverse proxy that I set up in front of FusionAuth.

Hi!

Today, when I restarted my FusionAuth server the following 500 error was thrown:
io.fusionauth.app.primeframework.error.ExceptionExceptionHandler - An unhandled exception was thrown
2021-02-19T12:33:25.901133267Z java.lang.UnsupportedOperationException: You are attempting to map a form field that contains multiple parameters to a property on the action class that is of type java.net.URI. This isn't allowed.
2021-02-19T12:33:25.901164240Z at org.primeframework.mvc.parameter.convert.converters.URIConverter.stringsToObject(URIConverter.java:57)
2021-02-19T12:33:25.901173143Z at org.primeframework.mvc.parameter.convert.AbstractGlobalConverter.convertFromStrings(AbstractGlobalConverter.java:89)
2021-02-19T12:33:25.901179950Z at org.primeframework.mvc.parameter.el.Accessor.convert(Accessor.java:152)
2021-02-19T12:33:25.901186348Z at org.primeframework.mvc.parameter.el.MemberAccessor.set(MemberAccessor.java:133)
2021-02-19T12:33:25.901193307Z at org.primeframework.mvc.parameter.el.Accessor.set(Accessor.java:90)
2021-02-19T12:33:25.901199032Z at org.primeframework.mvc.parameter.el.Expression.setCurrentValue(Expression.java:93)
2021-02-19T12:33:25.901205133Z at org.primeframework.mvc.parameter.el.DefaultExpressionEvaluator.setValue(DefaultExpressionEvaluator.java:132)
2021-02-19T12:33:25.901215115Z at org.primeframework.mvc.parameter.DefaultParameterHandler.setValues(DefaultParameterHandler.java:205)
2021-02-19T12:33:25.901222236Z at org.primeframework.mvc.parameter.DefaultParameterHandler.handle(DefaultParameterHandler.java:121)
2021-02-19T12:33:25.901250341Z at org.primeframework.mvc.parameter.DefaultParameterWorkflow.perform(DefaultParameterWorkflow.java:54)
2021-02-19T12:33:25.901257749Z at org.primeframework.mvc.workflow.SubWorkflowChain.continueWorkflow(SubWorkflowChain.java:51)
2021-02-19T12:33:25.901264389Z at org.primeframework.mvc.parameter.DefaultURIParameterWorkflow.perform(DefaultURIParameterWorkflow.java:102)
2021-02-19T12:33:25.901270866Z at org.primeframework.mvc.workflow.SubWorkflowChain.continueWorkflow(SubWorkflowChain.java:51)
2021-02-19T12:33:25.901277173Z at org.primeframework.mvc.scope.DefaultScopeRetrievalWorkflow.perform(DefaultScopeRetrievalWorkflow.java:58)
2021-02-19T12:33:25.901283463Z at org.primeframework.mvc.workflow.SubWorkflowChain.continueWorkflow(SubWorkflowChain.java:51)
2021-02-19T12:33:25.901290026Z at org.primeframework.mvc.message.DefaultMessageWorkflow.perform(DefaultMessageWorkflow.java:44)
2021-02-19T12:33:25.901307114Z at org.primeframework.mvc.workflow.SubWorkflowChain.continueWorkflow(SubWorkflowChain.java:51)
2021-02-19T12:33:25.901328377Z at io.fusionauth.app.primeframework.FrontEndTenantWorkflow.perform(FrontEndTenantWorkflow.java:183)
2021-02-19T12:33:25.901331919Z at org.primeframework.mvc.workflow.SubWorkflowChain.continueWorkflow(SubWorkflowChain.java:51)
2021-02-19T12:33:25.901335271Z at org.primeframework.mvc.action.DefaultActionMappingWorkflow.perform(DefaultActionMappingWorkflow.java:126)
2021-02-19T12:33:25.901338621Z at org.primeframework.mvc.workflow.SubWorkflowChain.continueWorkflow(SubWorkflowChain.java:51)
2021-02-19T12:33:25.901342429Z at org.primeframework.mvc.workflow.StaticResourceWorkflow.perform(StaticResourceWorkflow.java:97)
2021-02-19T12:33:25.901345831Z at org.primeframework.mvc.workflow.SubWorkflowChain.continueWorkflow(SubWorkflowChain.java:51)
2021-02-19T12:33:25.901349211Z at org.primeframework.mvc.parameter.RequestBodyWorkflow.perform(RequestBodyWorkflow.java:89)
2021-02-19T12:33:25.901352531Z at org.primeframework.mvc.workflow.SubWorkflowChain.continueWorkflow(SubWorkflowChain.java:51)
2021-02-19T12:33:25.901355877Z at org.primeframework.mvc.security.DefaultSavedRequestWorkflow.perform(DefaultSavedRequestWorkflow.java:64)
2021-02-19T12:33:25.901359311Z at org.primeframework.mvc.workflow.SubWorkflowChain.continueWorkflow(SubWorkflowChain.java:51)
2021-02-19T12:33:25.901362612Z at io.fusionauth.app.primeframework.CORSFilter.doFilter(CORSFilter.java:240)
2021-02-19T12:33:25.901366026Z at io.fusionauth.app.primeframework.CORSRequestWorkflow.perform(CORSRequestWorkflow.java:48)
2021-02-19T12:33:25.901369307Z at org.primeframework.mvc.workflow.SubWorkflowChain.continueWorkflow(SubWorkflowChain.java:51)
2021-02-19T12:33:25.901372602Z at io.fusionauth.app.primeframework.FusionAuthMVCWorkflow.perform(FusionAuthMVCWorkflow.java:88)
2021-02-19T12:33:25.901375987Z at org.primeframework.mvc.workflow.DefaultWorkflowChain.continueWorkflow(DefaultWorkflowChain.java:44)
2021-02-19T12:33:25.901379372Z at org.primeframework.mvc.servlet.FilterWorkflowChain.continueWorkflow(FilterWorkflowChain.java:50)
2021-02-19T12:33:25.901383017Z at org.primeframework.mvc.servlet.PrimeFilter.doFilter(PrimeFilter.java:78)
2021-02-19T12:33:25.901386369Z at com.inversoft.maintenance.servlet.MaintenanceModePrimeFilter.doFilter(MaintenanceModePrimeFilter.java:59)
2021-02-19T12:33:25.901399570Z at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
2021-02-19T12:33:25.901403420Z at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
2021-02-19T12:33:25.901406768Z at com.inversoft.servlet.UTF8Filter.doFilter(UTF8Filter.java:27)
2021-02-19T12:33:25.901410612Z at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
2021-02-19T12:33:25.901414032Z at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
2021-02-19T12:33:25.901421502Z at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:199)
2021-02-19T12:33:25.901424982Z at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96)
2021-02-19T12:33:25.901428243Z at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:543)
2021-02-19T12:33:25.901431497Z at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:139)
2021-02-19T12:33:25.901434852Z at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:81)
2021-02-19T12:33:25.901438095Z at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:87)
2021-02-19T12:33:25.901441368Z at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343)
2021-02-19T12:33:25.901444597Z at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:615)
2021-02-19T12:33:25.901447943Z at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65)
2021-02-19T12:33:25.901451192Z at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:818)
2021-02-19T12:33:25.901454453Z at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1626)
2021-02-19T12:33:25.901457783Z at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
2021-02-19T12:33:25.901461117Z at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1130)
2021-02-19T12:33:25.901464460Z at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:630)
2021-02-19T12:33:25.901478118Z at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
2021-02-19T12:33:25.901481558Z at java.base/java.lang.Thread.run(Thread.java:832)

I'm using Fusionauth on docker.

Does anyone know how to solve this? I already double-checked the configuration and its the same as it was yesterday.

Thank you!