Bug reported by customer about non working Heatmaps on IIS:

I get an error when after installing the HeatMap plugin and creating my first recording.
It says:Requesting 'https://piwik.X/plugins/HeatmapSessionRecording/configs.php?idsite=1&trackerid=5lX6EM&url=http%3A%2F%2Ftest.test%2F' resulted in an error: curl_exec: connection timed out after 2016 milliseconds. hostname requested was: piwik.X. As a result, tracking Heatmaps and Session Recordings may not work. You may need to change your webserver configuration to allow access to this file via the Internet or Intranet.

Solution

This modification will work for everyone who uses IIS.
The file I have modified is the web.config in the plugins-folder.
The only thing I've added is this part:

<alwaysAllowedUrls>
<add url="/plugins/HeatmapSessionRecording/configs.php" />
</alwaysAllowedUrls>

And the whole file with looks now like this after the changes:

<?xml version="1.0" encoding="UTF-8"?>

<configuration>

<system.webServer>

<security>

<requestFiltering>

<denyUrlSequences>

<add sequence=".php" />

</denyUrlSequences>

<alwaysAllowedUrls>

<add url="/plugins/HeatmapSessionRecording/configs.php" />

</alwaysAllowedUrls>

</requestFiltering>

</security>

</system.webServer>

</configuration>