Whistleblower Protection Reform Act of 2021 This bill expands and revises whistleblower protections applicable to individuals who provide information to the Securities and Exchange Commission (SEC) relating to a violation of securities laws. The prohibition of retaliation against whistleblowers is expanded to include individuals who provide information regarding potential violations to supervisors or other employees in positions of authority, including as part of their job duties. Additionally, the bill establishes the burden of proof regarding an unfavorable personnel action against a whistleblower, including evidence needed to prove that the whistleblower's conduct was a contributing factor in such an action. The bill also deems as unenforceable a predispute arbitration agreement regarding such an action and makes additional categories of sanctions eligible for distribution as part of whistleblower awards.