Task: Categorize the tweet's emotional expression, classifying it as either 'neutral or no emotion' or as one or more of the specified emotions (anger, anticipation, disgust, fear, joy, love, optimism, pessimism, sadness, surprise, trust) that reflect the tweeter's state of mind.
Tweet: They are building a shell command on a server, combining that with user input, and then executing that in a shell on the client. #shudder
This tweet contains emotions: 
fear, joy