I had written a pre-update plugin, it was working properly on my environment.
But after sending it across to the client, after he had deployed it we started getting the below mentioned error.
“XmlException: An error occurred while parsing EntityName”
We were actually passing secure configuration information to the plugin in the following format
And the issue was the password that was being used, it had ‘&’ character, which we then replaced with ‘&’ and the error got resolved.
Hope it helps!