validating javascript?

https://validator.w3.org/check?uri=http%3A%2F%2Fwww.sekhu.net%2Fwp%2F&charset=%28detect+automatically%29&doctype=%28detect+automatically%29&ss=1&outline=1&verbose=1

I’m getting an error when validating the page. The error comes up:

Line 74, column 71: duplicate specification of attribute "onsubmit"

...c8e97b5609eb88dffb1464');" onsubmit="return liveSearchSubmit()" id="searchfo

Is that to say I can’t have 2 onsubmit values? How would I go about fixing it, without borking the plugin? It’s part of the livesearch code.