Weasel is a common slang term for such a person. Urban Dictionary entries lightly edited for grammar and spelling:

• Shifty, scheming person that will do whatever they need to to escape whatever they fear in the moment.

 
• A cunning, sneaky person. On internet forums they are often a liar, fake or poser. Will try to extract information from you to share with others and / or use it against you. Uses shiftiness to evade an obligation, commitment or duty. They will make promises then renege on them.

 
• One who is particularly cunning, conniving, shifty, sneaky, scheming and down right sly. Weasels are known for their ability to adapt to any situation and to manipulate it to suit their own weasel ways.

The term is especially appropriate to describe somebody who twists the truth to get something they want or to evade responsibility. There's also a term for the kind of equivocations that weasels use to twist the truth: weasel words. Many style guides exhort writers to avoid weasel words.

Weasel is a common slang term for such a person. Urban Dictionary entries lightly edited for grammar and spelling:

• Shifty, scheming person that will do whatever they need to to escape whatever they fear in the moment.

• A cunning, sneaky person. On internet forums they are often a liar, fake or poser. Will try to extract information from you to share with others and / or use it against you. Uses shiftiness to evade an obligation, commitment or duty. They will make promises then renege on them.

• One who is particularly cunning, conniving, shifty, sneaky, scheming and down right sly. Weasels are known for their ability to adapt to any situation and to manipulate it to suit their own weasel ways.

The term is especially appropriate to describe somebody who twists the truth to get something they want or to evade responsibility. There's also a term for the kind of equivocations that weasels use to twist the truth: weasel words. Many style guides exhort writers to avoid weasel words.