Error In Page

Error Message: Detected a potentially dangerous character in a query string paramater. Name = "><script>alert(1)</script>

Stack Trace:
System.Exception: Detected a potentially dangerous character in a query string paramater. Name = "><script>alert(1)</script>
at Dea.Web.Sites.MasterCalendar.BasePage.BasePage_PreInit(Object sender, EventArgs e)
at System.Web.UI.Page.OnPreInit(EventArgs e)
at Dea.Web.Core.BasePage.OnPreInit(EventArgs e)
at System.Web.UI.Page.PerformPreInit()
at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)

Additional Information
ErrorCaughtBy: RSSFeeds.aspx
PatchNumber: 201805210
ClientName:
Product: