Function seems to be receiving malformed binary request data

Support
2

Your function needs to be:

export async function handler({body}) {
  return {
    statusCode: 200,
    body: Buffer.from(body, 'base64').toString('utf8')
  };
}

Because of:

Demo: https://quirky-mirzakhani-33e90a.netlify.app/

Note that, the above would return the decoded string so example com in your case.