System1 (SST) CPO has 377 shares withheld to cover RSU taxes on vesting

Rhea-AI Filing Summary

System1, Inc.'s Chief People Officer Elizabeth Sestanovich reported an automatic share withholding tied to restricted stock vesting. On 01/15/2026, 670 previously granted restricted stock units vested, and the company withheld 377 shares of Class A common stock at $4.40 per share to cover her tax withholding obligation rather than conducting an open-market sale. After this transaction, she beneficially owned 59,500 shares of Class A common stock, which includes 43,055 unvested restricted stock units. This reflects routine equity award administration rather than a discretionary stock sale.

SEC Form 4

FORM 4

UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP

Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934
or Section 30(h) of the Investment Company Act of 1940

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Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

Check this box to indicate that a transaction was made pursuant to a contract, instruction or written plan for the purchase or sale of equity securities of the issuer that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c). See Instruction 10.

1. Name and Address of Reporting Person^*

Sestanovich Elizabeth

(Last) (First) (Middle)

4235 REDWOOD AVE

(Street)

LOS ANGELES CA 90066

(City) (State) (Zip)

2. Issuer Name and Ticker or Trading Symbol
System1, Inc. [ SST ]

5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)

	Director		10% Owner
X	Officer (give title below)		Other (specify below)
	Chief People Officer

3. Date of Earliest Transaction (Month/Day/Year)
01/15/2026

4. If Amendment, Date of Original Filed (Month/Day/Year)

6. Individual or Joint/Group Filing (Check Applicable Line)

X	Form filed by One Reporting Person
	Form filed by More than One Reporting Person

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1. Title of Security (Instr. 3)	2. Transaction Date (Month/Day/Year)	2A. Deemed Execution Date, if any (Month/Day/Year)	3. Transaction Code (Instr. 8)		4. Securities Acquired (A) or Disposed Of (D) (Instr. 3, 4 and 5)			5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4)	6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	7. Nature of Indirect Beneficial Ownership (Instr. 4)
			Code	V	Amount	(A) or (D)	Price
Class A Common Stock	01/15/2026		F		377(1)	D	$4.4	59,500(2)	D

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security (Instr. 3)	2. Conversion or Exercise Price of Derivative Security	3. Transaction Date (Month/Day/Year)	3A. Deemed Execution Date, if any (Month/Day/Year)	4. Transaction Code (Instr. 8)		5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5)		6. Date Exercisable and Expiration Date (Month/Day/Year)		7. Title and Amount of Securities Underlying Derivative Security (Instr. 3 and 4)		8. Price of Derivative Security (Instr. 5)	9. Number of derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4)	10. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	11. Nature of Indirect Beneficial Ownership (Instr. 4)
				Code	V	(A)	(D)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares

Explanation of Responses:

1. Upon the vesting of 670 restricted stock units ("RSUs") previously granted to the reporting person, the Company withheld 377 shares to cover the reporting person's tax withholding obligation with respect to the vesting of such RSUs.

2. Includes 43,055 unvested RSUs.

Remarks:

	/s/ Daniel Weinrot, Attorney-in-Fact for Elizabeth Sestanovich	01/16/2026
	** Signature of Reporting Person	Date
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
* If the form is filed by more than one reporting person, see Instruction 4 (b)(v).
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.
Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB Number.

FAQ

What insider transaction did System1 (SST) report for Elizabeth Sestanovich?

The filing shows that on 01/15/2026, Chief People Officer Elizabeth Sestanovich had 377 shares of Class A common stock withheld by System1, Inc. to satisfy tax withholding on the vesting of restricted stock units.

Was the System1 (SST) Form 4 transaction an open-market sale?

No. The Form 4 reports a code “F” transaction, meaning 377 shares were withheld by the company to cover taxes when 670 restricted stock units vested, rather than sold on the open market.

How many System1 (SST) shares does Elizabeth Sestanovich hold after this transaction?

Following the reported transaction, Elizabeth Sestanovich beneficially owned 59,500 shares of System1 Class A common stock.

How many unvested restricted stock units does the System1 CPO have?

The footnotes state that her holdings include 43,055 unvested restricted stock units (RSUs).

What does transaction code "F" mean in this System1 (SST) Form 4?

Code “F” indicates the company withheld shares from vested equity awards to satisfy the reporting person’s tax withholding obligation.

What was the price used for the tax withholding shares in the System1 Form 4?

The 377 withheld shares of Class A common stock were valued at $4.40 per share for tax withholding purposes.