This was actually supposed to be fixed in #18794 but seems to be still a problem. It is the same URL as in #18794 . Or is it a regression?

Error: {"message":"strpos(): Argument #1 ($haystack) must be of type string, array given","file":"/core/Period/Range.php","line":535,"request_id":"f2aab","backtrace":" on /core/Period/Range.php(535)\n#0 /core/Period/Range.php(535): strpos(Array, '-')\n#1 /plugins/ImageGraph/ImageGraph.php(91): Piwik\Period\Range::getRelativeToEndDate('day', 'last30', Array, Object(Piwik\Site))\n#2 [internal function]: Piwik\Plugins\ImageGraph\ImageGraph->getReportMetadata(Array, Array)\n#3 /core/EventDispatcher.php(147): call_user_func_array(Array, Array)\n#4 /core/Piwik.php(871): Piwik\EventDispatcher->postEvent('API.getReportMe...', Array, false, Array)\n#5 /plugins/API/ProcessedReport.php(220): Piwik\Piwik::postEvent('API.getReportMe...', Array)\n#6 /plugins/API/API.php(272): Piwik\Plugins\API\ProcessedReport->getReportMetadata('1', 'day', Array, false, false)\n#7 /core/Plugin/Controller.php(430): Piwik\Plugins\API\API->getReportMetadata('1', 'day', Array)\n#8 /plugins/VisitsSummary/Controller.php(119): Piwik\Plugin\Controller->getLastUnitGraphAcrossPlugins('VisitsSummary', 'getEvolutionGra...', false, Array, 'This is an over...')\n#9 [internal function]: Piwik\Plugins\VisitsSummary\Controller->getEvolutionGraph()\n#10 /core/FrontController.php(631): call_user_func_array(Array, Array)\n#11 /core/FrontController.php(169): Piwik\FrontController->doDispatch('VisitsSummary', 'getEvolutionGra...', Array)\n#12 /core/dispatch.php(32): Piwik\FrontController->dispatch()\n#13 /index.php(25): require_once('/c...')\n#14 {main}","safemode_backtrace":"#0 [internal function]: Piwik\Plugins\Cloud\Controller->safemode(Array)\n#1 /core/FrontController.php(631): call_user_func_array(Array, Array)\n#2 /core/FrontController.php(169): Piwik\FrontController->doDispatch('Cloud', 'safemode', Array)\n#3 /core/FrontController.php(100): Piwik\FrontController->dispatch('CorePluginsAdmi...', 'safemode', Array)\n#4 /core/FrontController.php(140): Piwik\FrontController::(Array)\n#5 /core/FrontController.php(190): Piwik\FrontController::(Object(TypeError))\n#6 /core/dispatch.php(32): Piwik\FrontController->dispatch()\n#7 /index.php(25): require_once('/c...')\n#8 {main}"}

URL: https://demo.matomo.cloud/index.php?action=getEvolutionGraph&date%5B0%5D=exp&date%5B1%5D=%3D1%E9%8E%88%27%22%5C%28&disableLink=0&forceView=1&idSite=1&module=VisitsSummary&period=day&viewDataTable=graphEvolution&widget=1

GET: {"action":"getEvolutionGraph","date":["exp","=1\u9388'"\("],"disableLink":"0","forceView":"1","idSite":"1","module":"VisitsSummary","period":"day","viewDataTable":"graphEvolution","widget":"1"}