Mediaalpha (MAX): White Mountains Insurance Group, Ltd. cut its MAX stake to 24.3% from 35.1% 24.3%

24.3%

Stake · was 35.1%

12.4M

Shares owned

Stake as of

Nov 4, 2026

Filed

Nov 5, 2026

The story around this disclosure

Every dated public record OQRO holds about the company from 60 days before to 120 days after, oldest first. It shows what was going on; none of it is a stated reason for the trade.

1. Sep 9, 2026Company filing · Form 8-K · Material agreementSigned an important agreement
2. Sep 21, 2026Insider · 1 personInsiders: 2 sales (~$81K)
3. Sep 22, 2026Insider · 1 personInsiders: 2 sales (~$83K)
4. Sep 25, 2026InsiderOfficer sold ~$28K of MAX shares in the open market
5. Oct 1, 2026Government · Federal Register proposed ruleRule on Impersonation of Government and Businesses
6. Oct 8, 2026InsiderDirector sold ~$241K of MAX shares in the open market
7. Oct 9, 2026InsiderDirector sold ~$22K of MAX shares in the open market
8. Oct 12, 2026Insider · 1 personInsiders: 2 sales (~$78K)
9. Oct 13, 2026Insider · 1 personInsiders: 2 sales (~$78K)
10. Oct 14, 2026Insider · 1 personInsiders: 2 sales (~$80K)
11. Oct 16, 2026InsiderOfficer sold ~$35K of MAX shares in the open market
12. Oct 19, 2026Insider · 2 peopleInsiders: 3 sales (~$242K)
13. Oct 20, 2026Insider · 1 personInsiders: 2 sales (~$108K)
14. Oct 21, 2026Insider · 1 personInsiders: 2 sales (~$107K)
15. Oct 26, 2026Insider · 1 personInsiders: 2 sales (~$109K)
16. Oct 27, 2026Insider · 1 personInsiders: 2 sales (~$139K)
17. Oct 28, 2026Company filing · Form 8-K · ResultsReported its results
18. Oct 28, 2026Insider · 1 personInsiders: 2 sales (~$107K)
19. Oct 30, 20265% stakeWhite Mountains Insurance Group, Ltd. filed an activist stake (13D) of 35.1%
20. Oct 30, 2026InsiderOfficer sold ~$362K of MAX shares in the open market
21. Nov 2, 2026Insider · 3 peopleInsiders: 4 sales (~$5.2M)
22. Nov 3, 2026Insider · 2 peopleInsiders: 3 sales (~$4.6M)
23. Nov 4, 2026Insider · 3 peopleInsiders: 4 sales (~$80.3M)

What came next

1. Nov 5, 20265% stakeWhite Mountains Insurance Group, Ltd. filed an activist stake (13D) of 24.3%

How to read SEC Schedule 13D

A Schedule 13D and a Schedule 13G both disclose beneficial ownership of more than 5% of a US company's voting shares. A 13D is the long form, filed by holders who may seek to influence or control the company, and it must state what they intend to do. A 13G is the short form, open only to passive holders and to certain institutions holding in the ordinary course of business, and it asks no question about intent.

Full guide: Schedule 13D vs Schedule 13G: what is the difference?

What else is on file for Mediaalpha

For Mediaalpha, OQRO holds 50 insider filings (SEC Form 4 or Form 144) and 3 fund holdings reports (13F) dated in the last 90 days.

These are records OQRO holds, counted by their date, not a measure of how much trading took place. Routine paperwork such as option exercises and tax withholding is left out. Everything for the company is on its MAX page.

How this filing works

• Schedule 13D vs 13G

Other disclosures at Mediaalpha

• SEC Form 4Nov 6, 2026
• SEC Form 4Nov 5, 2026
• SEC Form 4Nov 5, 2026
• SEC Form 4Nov 5, 2026
• SEC Form 4Nov 5, 2026
• SEC Form 4Nov 5, 2026

Everything OQRO holds on this company is on its MAX page.