https://www.law.cornell.edu/rules/fre/rule_502
Rule 502. Attorney-Client Privilege and Work Product; Limitations on Waiver
The following provisions apply, in the circumstances set out, to disclosure of a communication or information covered by the attorney-client privilege or work-product protection.
(a) Disclosure Made in a Federal Proceeding or to a Federal Office or Agency; Scope of a Waiver. When the disclosure is made in a federal proceeding or to a federal office or agency and waives the attorney-client privilege or work-product protection, the waiver extends to an undisclosed communication or information in a federal or state proceeding only if:
(1) the waiver is intentional;
(2) the disclosed and undisclosed communications or information concern the same subject matter; and
(3) they ought in fairness to be considered together.
(b) Inadvertent Disclosure. When made in a federal proceeding or to a federal office or agency, the disclosure does not operate as a waiver in a federal or state proceeding if:
(1) the disclosure is inadvertent;
(2) the holder of the privilege or protection took reasonable steps to prevent disclosure; and
(3) the holder promptly took reasonable steps to rectify the error, including (if applicable) following Federal Rule of Civil Procedure 26 (b)(5)(B).
(c) Disclosure Made in a State Proceeding. When the disclosure is made in a state proceeding and is not the subject of a state-court order concerning waiver, the disclosure does not operate as a waiver in a federal proceeding if the disclosure:
(1) would not be a waiver under this rule if it had been made in a federal proceeding; or
(2) is not a waiver under the law of the state where the disclosure occurred.