Sensitive s Key

​ I went to answer an instant message about 10 minutes ago and all of a sudden my "S" key is very sensitive. If I even lightly press it it types one or more "s" letters without me wanting it to. The problem is at its worst if I touch the right side of the "s" key. ​

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​ It still types one (and mostly only one) s if I press down on it normally. It was working fine before that and I have not spilled liquid or anything on it. ​