to disguise as someone else and promote one’s work/opinion; to attack oneself and play the victim
A typical 自作自演 is to support or promote one’s work or ideas using multiple accounts on social media/web forums.
If you think someone is doing 自作自演, you can say “自演乙 (じえんおつ)”, meaning “自作自演お疲(つか)れ様(さま)”, i.e. “Well done on your 自作自演!”. However, this expression also has a very slang, internet-jargonish tone, and is getting outdated nowadays.
A lot of people disguise themselves as someone else and promote their work or ideas on internet forums.