We are developing a .NET application using Visual Studio 2010 (Version 10.0.30319.1), on .NET Framework 4.0.30319.
Several aspx pages within our application include the following code:
window.onbeforeunload = Close;
with the Close() function handling some common cleanup logic. This has been behaving correctly for many years, meaning that the function is executed only when the user closes the page. Recently however, with the installation of security update 2846071, (July 9,2103) we are experiencing the unexpected invocation of this event when clicking on one or more buttons on the page. None of the code has changed, only the Service Pack update.
Is there anything within this Service Pack that would cause the onbeforeunload event to fire, when it would not have in the past?
This seems to impact users using I.E.9 or I.E.10 (I.E.10 running in compatible View)
If the update is rolled back then the issue cannot be reproduced.