Quick question

Was servicing the car yesterday as it was missfireing and needed a service when i took out the spark plug leads the end that attaches to the plug there was a bitof oil on it and when i took out all the spark plugs they were all covered in oil as if it was spitting up around them. Any ideas what this would be ?? was thinking that the last person to service it might just not have tightened them proper

There is a gasket there, can't remember the name on it but it went recently in a mate if mines car, was a handy enough fix but a bit fiddley