Magnite (MGNI) CTO has 8K shares withheld for taxes, still holds 252K

Rhea-AI Filing Summary

MAGNITE, INC. (MGNI) reported that Chief Technology Officer David Buonasera had 8,102 shares of common stock withheld on August 15, 2026 at $24.73 per share. The shares were a non-discretionary forfeiture to cover tax withholding obligations tied to vesting restricted stock units, leaving him with 252,734 shares held directly.

Insider Trade Summary

Net Seller: 8,102 shares

Net Sell 1 txn

Insider Buonasera David

Role CHIEF TECHNOLOGY OFFICER

Type	Security	Shares	Price	Value
Tax Withholding	Common Stock F1	8,102	$24.73	$200K

Holdings After Transaction: Common Stock — 252,734 shares (Direct)

Footnotes (1)

1. F1. Represents the non-discretionary forfeiture of shares on behalf of the Reporting Person pursuant to an arrangement mandated by the Issuer to cover the tax withholding obligations associated with the vesting of restricted stock units.

Key Figures

Shares forfeited for taxes: 8,102 shares Reference price per share: $24.73 Shares owned after transaction: 252,734 shares +1 more

4 metrics

Shares forfeited for taxes 8,102 shares Non-discretionary forfeiture on August 15, 2026 to cover tax withholding

Reference price per share $24.73 Price per share reported for the tax-withholding disposition

Shares owned after transaction 252,734 shares Direct holdings of MAGNITE, INC. common stock following the forfeiture

Transaction date August 15, 2026 Date of the tax-withholding disposition reported on Form 4

Key Terms

restricted stock units, non-discretionary forfeiture, tax withholding obligations

3 terms

restricted stock units financial

"associated with the vesting of restricted stock units"

Restricted stock units are a type of company reward where employees are promised shares of stock, but they only fully own these shares after meeting certain conditions, like staying with the company for a set time. They matter because they can become valuable assets and are often used to motivate employees to help the company succeed.

non-discretionary forfeiture financial

"Represents the non-discretionary forfeiture of shares on behalf"

tax withholding obligations financial

"to cover the tax withholding obligations associated with the vesting"

FAQ

What insider transaction did MGNI report for CTO David Buonasera?

MAGNITE, INC. reported 8,102 shares of common stock were withheld from CTO David Buonasera on August 15, 2026 to cover tax withholding obligations related to vesting restricted stock units, at a reference price of $24.73 per share.

Was the MGNI Form 4 transaction an open-market sale?

No. The Form 4 states the 8,102 shares represented a non-discretionary forfeiture mandated by MAGNITE, INC. to satisfy tax withholding obligations from vesting restricted stock units, rather than a voluntary open-market sale by the executive.

How many MGNI shares does CTO David Buonasera hold after this transaction?

After the tax-withholding forfeiture of 8,102 shares, CTO David Buonasera directly holds 252,734 shares of MAGNITE, INC. common stock, as reported in the Form 4 following the August 15, 2026 transaction.

What does transaction code F mean in the MGNI Form 4?

Transaction code F indicates shares were used for payment of tax liability or exercise price. Here, the filing specifies a non-discretionary forfeiture to cover tax withholding obligations from vesting restricted stock units for the reporting person.

Was a Rule 10b5-1 plan involved in this MGNI insider transaction?

No. The filing shows the Rule 10b5-1 checkbox is not affirmed, and the footnote explains the 8,102-share forfeiture was mandated by MAGNITE, INC. to cover tax withholding on vesting restricted stock units, not executed under a trading plan.

AI-generated analysis. How Rhea-AI works. Not financial advice.

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Form 4 Insider Transactions: What Each Field Means →

Available on EDGAR 08/18/2026 - 04:25 PM Accepted by SEC EDGAR 08/18/2026 - 04:25 PM Learn about SEC filing dates

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

OMB APPROVAL

OMB Number:			3235-0287
Estimated average burden
hours per response:			0.5

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^*

Buonasera David

(Last) (First) (Middle)

C/O MAGNITE, INC.

1250 BROADWAY, 9TH FLOOR

(Street)

NEW YORK NEW YORK 10001

(City) (State) (Zip)

UNITED STATES

(Country)

2. Issuer Name and Ticker or Trading Symbol
MAGNITE, INC. [ MGNI ]

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

	Director		10% Owner
X	Officer (give title below)		Other (specify below)
	CHIEF TECHNOLOGY OFFICER

2a. Foreign Trading Symbol

3. Date of Earliest Transaction (Month/Day/Year)
08/15/2026

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

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

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

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
Common Stock	08/15/2026		F(1)		8,102	D	$24.73	252,734	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. Represents the non-discretionary forfeiture of shares on behalf of the Reporting Person pursuant to an arrangement mandated by the Issuer to cover the tax withholding obligations associated with the vesting of restricted stock units.

Remarks:

	/s/ Aaron Saltz, attorney-in-fact	08/18/2026
	** 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.
* Form 4: SEC 1474 (03-26)