Filed pursuant to Rule 424(b)(3)
Registration No. 333-262608
PROSPECTUS SUPPLEMENT NO. 3
(to prospectus dated
April 18, 2022)
Up to 25,483,334 Shares of Class A Common Stock Issuable Upon
Exercise of Warrants
Up
to 106,508,061 Shares of Common Stock
Up to 8,424,034 Warrants
This prospectus supplement is being filed to update and supplement the information contained in the prospectus dated April 18, 2022 (the
Prospectus), related to the issuance by us of up to an aggregate of up to 25,483,334 shares of our Class A common stock, $0.0001 par value per share (Class A Common Stock), which consists of (i) up to 8,233,334
shares of Class A Common Stock that are issuable upon the exercise of 8,233,334 warrants (the Private Placement Warrants) originally issued in a private placement at a price of $1.50 per warrant in connection with the initial public
offering of Trebia Acquisition Corp., a Cayman Islands exempted company (Trebia), and (ii) up to 17,250,000 shares of Class A Common Stock that are issuable upon the exercise of 17,250,000 warrants (the Public
Warrants, and together with the Private Placement Warrants, the Warrants) originally issued in the initial public offering of units of Trebia at a price of $10.00 per unit, with each unit consisting of one Class A ordinary
share and one-third of one warrant. Each Warrant entitles the holder thereof to purchase one share of our Class A Common Stock at a price of $11.50 per share. On April 19, 2022, the holders of the
Private Placement Warrants exercised them in full on a cashless basis in accordance with the terms of the Private Placement Warrants, which resulted in the net issuance of an aggregate of 3,532,372 shares of our Class A Common Stock in full
settlement of the Private Placement Warrants. We will receive the proceeds from any exercise of any Public Warrants for cash, which amount of aggregate proceeds, assuming the exercise of all Public Warrants, could be up to $198.4 million. We
believe the likelihood that holders of the Public Warrants will exercise their Warrants, and therefore the amount of cash proceeds that we would receive, is dependent upon the market price of our Class A Common Stock. If the market price for
our Class A Common Stock is less than $11.50 per share, we believe holders of the Public Warrants will be unlikely to exercise their Warrants.
The Prospectus also relates to the offer and sale from time to time by the selling securityholders (including their transferees, donees,
pledgees and other successors-in-interest) named in the Prospectus (collectively, the Selling Securityholders) of (a) 106,508,061 shares of Class A
Common Stock (the Total Resale Shares), consisting of (i) 48,224,485 shares held directly by the Selling Securityholders, (ii) 22,077,319 shares of Class A Common Stock issuable to unitholders of S1 Holdco, LLC upon the redemption
of their S1 Holdco Class B Units (and the corresponding exchange of their Class C common stock) (as defined in the Prospectus), (iii) 1,450,000 shares issuable from fully vested restricted stock units of the Company granted to Michael
Blend and Just Develop It Limited (which, in the case of clauses (i), (ii) and (iii) above, were issued as equity merger consideration to securityholders of S1 Holdco, LLC and System1 SS Protect Holdings, Inc. and their respective subsidiaries
and affiliates, pursuant to the Business Combination Agreement (as defined in the Prospectus) at an equity consideration value of $10.00 per share), (iv) 24,648,446 shares issued to Cannae Holdings, Inc. (Cannae) in connection with the
Business Combination Agreement, Sponsor Agreement (as defined in the Prospectus) and Backstop Agreement (as defined in the Prospectus) at a price of $10.00 per share, (v) 2,533,324 shares issued to Cannae and 1,000,000