Regex match for HTML tag containing “on” JS trigger

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C#

regular-expression

I want to check if an HTML tag (potentially split across multiple lines) contains an "on" JS trigger.  The actual HTML tag and the Javascript are of no consequence.  For example:

<img src="foo.jpg"  önblur="foo()"/>Other stuff

I've got most of this to work using the pattern:

<\w+([^>])+?(on\w+)+[\s\S]+?>

However, this also matches:

<p style="font-size:11px;">Other stuff</p>

I modified the original pattern to:

<\w+([^>])+?(\s)+(on\w+)+[\s\S]+?>

While this fixes the false positive, it requires the "onsomething" keyword to be preceded by 2 or more whitespace characters for a match to occur.  A nudge in the right direction would be appreciated.

/ravi