X0202 SCHEDULE 13D/A 0000776867 XXXXXXXX LIVE 8 Class A Common Stock, par value $0.01 per share 11/04/2026 false 0001818383 58450V104 MediaAlpha, Inc.

700 South Flower Street Suite 640 Los Angeles CA 90017

Robert L. Seelig, Esq. (603) 640-2200 23 South Main Street, Suite 3B Hanover NH 03755 0000776867 N White Mountains Insurance Group, Ltd. b AF N D0 900000.00 11456223.00 900000.00 11456223.00 12356223.00 N 24.3 HC 0001979065 N WM Hinson (Bermuda) Ltd. b WC N D0 0.00 11456223.00 0.00 11456223.00 11456223.00 N 22.5 CO Class A Common Stock, par value $0.01 per share MediaAlpha, Inc. 700 South Flower Street Suite 640 Los Angeles CA 90017 This Amendment No. 8 (this "Amendment No. 8") to the Schedule 13D filed with the Securities and Exchange Commission (the "Commission") on June 30, 2023 (as amended and supplemented from time to time, this "Schedule 13D") is being filed jointly by White Mountains Insurance Group, Ltd. ("White Mountains") and WM Hinson (Bermuda) Ltd. ("WM Hinson" and, together with White Mountains, the "Reporting Persons") with respect to the Class A Common Stock, par value $0.01 per share (the "Class A Shares"), of MediaAlpha, Inc., a Delaware corporation (the "Issuer"), beneficially owned by the Reporting Persons. The purpose of this Amendment No. 8 is to reflect the sale of 5,500,391 Class A Shares by WM Hinson pursuant to Rule 144 under the Securities Act of 1933, as amended ("Rule 144"). Except as set forth below, all Items of this Schedule 13D remain unchanged. Capitalized terms used in this Amendment No. 8 and not otherwise defined shall have the respective meanings assigned to such terms in this Schedule 13D. Item 4 is amended and supplemented as follows: On November 4, 2026, WM Hinson sold 5,500,391 Class A Shares to J.P. Morgan Securities LLC pursuant to Rule 144 at a price of $13.90 per share (the "Sale"). Following the Sale, the Reporting Persons beneficially own approximately 24.27% of the Class A Shares, based on 50,903,805 Class A Shares outstanding as of October 26, 2026, as reported in the Issuer's Form 10-Q filed with the Commission on October 28, 2026 (such number of Class A Shares issued and outstanding, the "Class A Shares Outstanding"). The purpose of the Sale was to monetize a portion of the Reporting Persons' ownership interest in the Issuer. Item 5(a)-(b) is amended and restated as follows: The information set forth on the cover pages of this Amendment No. 8, and the information set forth or incorporated by reference in Items 2, 3, 4 and 6 of this Schedule 13D are hereby incorporated by reference in this Item 5(a)-(b). As of the date hereof, White Mountains directly holds 900,000 Class A Shares of the Issuer and is the indirect beneficial owner of 11,456,223 Class A Shares directly held by its wholly owned direct subsidiary, WM Hinson, as presented herein. None of the Reporting Persons beneficially owns any shares of Class B Common Stock, par value $0.01 per share ("Class B Shares"). The Class A Shares held by the Reporting Persons represent approximately 24.27% of the Class A Shares Outstanding. As of the date hereof, and based on the knowledge of the Reporting Persons, the beneficial ownership of Class A Shares of the following persons listed in Annex A to this Schedule 13D (as amended and restated by the updated Annex A filed as Exhibit 99.5 to Amendment No. 7) is as follows: Robert L. Seelig holds 10,000 Class A Shares, which results in Mr. Seelig beneficially owning 10,000 Class A Shares, representing approximately 0.02% of the Class A Shares Outstanding; and John G. Sinkus holds 750 Class A Shares, which results in Mr. Sinkus beneficially owning 750 Class A Shares, representing less than 0.01% of the Class A Shares Outstanding. The beneficial ownership calculations set forth herein assume the exchange of any Class B Shares beneficially owned, together with a corresponding number of Class B-1 Units, for an equal number of Class A Shares pursuant to the Exchange Agreement. The percentage calculations set forth herein are based on 50,903,805 Class A Shares Outstanding as of October 26, 2026, as reported in the Issuer's Form 10-Q filed with the Commission on October 28, 2026, and are calculated in accordance with Rule 13d-3(d)(1)(i) under the Act. The filing of this Amendment No. 8 shall not be construed as an admission that any Reporting Person is the beneficial owner of any of the Class A Shares that such Reporting Person may be deemed to beneficially own. Without limiting the foregoing sentence, all of the Reporting Persons, other than with respect to Class A Shares directly held by such Reporting Person (or, in the case of White Mountains, directly held by WM Hinson) as described on each cover page to this Amendment No. 8, disclaim beneficial ownership of all Class A Shares reported in this Amendment No. 8. In addition, the filing of this Amendment No. 8 shall not be construed as an admission that any partner, member, director, officer or affiliate of any Reporting Person is the beneficial owner of any of the Class A Shares that such partner, member, director, officer or affiliate may be deemed to beneficially own. In addition, because of the relationships among White Mountains and WM Hinson, on the one hand, and the other Stockholders' Agreement Parties, on the other hand, as a result of the Stockholders' Agreement, the Reporting Persons may be deemed, pursuant to Rules 13d-3 and 13d-5 under the Act, to beneficially own the Class A Shares, Class B Shares or Class B-1 Units held in aggregate by the other Stockholders' Agreement Parties. Notwithstanding the foregoing, the filing of this Amendment No. 8 shall not be construed as an admission that any Reporting Person is the beneficial owner of any of the Class A Shares, Class B Shares or Class B-1 Units that such Reporting Person may be deemed to beneficially own. Further, each of the Reporting Persons disclaims membership in a group with each other Stockholders' Agreement Party. Same as (a) above. Item 5(c) is amended and supplemented as follows: On November 4, 2026, WM Hinson sold 5,500,391 Class A Shares to J.P. Morgan Securities LLC at $13.90 per share in the Sale described in Item 4. Item 6 is amended and supplemented as follows: The information set forth in Item 4 of this Amendment No. 8 is hereby incorporated by reference in this Item 6. In connection with the Sale, each of the Reporting Persons is subject to a 30-day lock-up with J.P. Morgan Securities LLC restricting transfers of its Class A Shares subject to certain exceptions. White Mountains Insurance Group, Ltd. /s/ Robert L. Seelig 11/05/2026 WM Hinson (Bermuda) Ltd. /s/ John G. Sinkus 11/05/2026