Magnite CTO sells 13,699 shares at $17–$19

Rhea-AI Filing Summary

MAGNITE, INC. Chief Technology Officer David Buonasera reported open-market sales of company Common Stock over three consecutive days. He sold 1,057 shares at $17.00, 11,233 shares at $18.00, and 1,409 shares at $19.00, totaling 13,699 shares.

Following these transactions, Buonasera directly holds 279,085 shares of Magnite common stock. The filing notes that the reported transactions were executed under a pre-arranged Rule 10b5-1 trading plan adopted on September 11, 2025, indicating they were scheduled in advance rather than timed discretionarily.

Insider Trade Summary 10b5-1

Net Seller: 13,699 shares

Net Sell 3 txns

Insider Buonasera David

Role CHIEF TECHNOLOGY OFFICER

Sold 13,699 shs ($247K)

Type	Security	Shares	Price	Value
Sale	Common Stock	1,409	$19.00	$27K
Sale	Common Stock	11,233	$18.00	$202K
Sale	Common Stock	1,057	$17.00	$18K

Holdings After Transaction: Common Stock — 279,085 shares (Direct)

Footnotes (1)

1. F1. The reported transaction was effected pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on September 11, 2025.

Key Figures

Total shares sold: 13,699 shares Shares sold on 2026-06-15: 1,057 shares at $17.00 Shares sold on 2026-06-16: 11,233 shares at $18.00 +2 more

5 metrics

Total shares sold 13,699 shares Open-market sales reported in Form 4

Shares sold on 2026-06-15 1,057 shares at $17.00 Common Stock sale

Shares sold on 2026-06-16 11,233 shares at $18.00 Common Stock sale

Shares sold on 2026-06-17 1,409 shares at $19.00 Common Stock sale

Shares held after transactions 279,085 shares Direct ownership following sales

Key Terms

Rule 10b5-1 trading plan, open-market sale, Common Stock

3 terms

Rule 10b5-1 trading plan regulatory

"The reported transaction was effected pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on September 11, 2025."

A Rule 10b5-1 trading plan is a pre-arranged schedule that allows company insiders to buy or sell stock at specific times, even if they have inside information. It helps prevent accusations of unfair trading by making these transactions look planned and transparent, rather than sneaky or illegal.

open-market sale financial

"transaction_action: open-market sale"

An open-market sale is when a shareholder sells existing shares directly on a public exchange to any willing buyer, rather than through a private deal. Think of it like putting goods on a busy market stall where price is set by supply and demand; for investors it matters because such sales increase available supply, can put short-term downward pressure on the stock price, and signal changes in liquidity or investor confidence.

Common Stock financial

"security_title: Common Stock"

Common stock represents ownership shares in a company, giving investors a stake in its success and a say in important decisions through voting rights. It is the most common type of stock traded on markets and can provide income through dividends, as well as potential for value growth. For investors, holding common stock means sharing in the company’s profits and risks.

FAQ

AI-generated questions and answers. How Rhea-AI works. Not financial advice.

What did Magnite (MGNI) CTO David Buonasera report in this Form 4?

Magnite CTO David Buonasera reported selling 13,699 shares of Common Stock in open-market transactions over three days, at prices between $17.00 and $19.00 per share, under a pre-arranged Rule 10b5-1 trading plan adopted on September 11, 2025.

How many Magnite (MGNI) shares did the CTO sell and at what prices?

David Buonasera sold 1,057 Magnite shares at $17.00, 11,233 shares at $18.00, and 1,409 shares at $19.00. In total, he disposed of 13,699 shares of Common Stock through open-market sales described in the Form 4 filing.

How many Magnite (MGNI) shares does the CTO hold after these sales?

After completing the reported transactions, CTO David Buonasera directly holds 279,085 shares of Magnite Common Stock. This post-transaction figure reflects his remaining direct ownership position as disclosed in the Form 4 insider trading report filed with regulators.

Were the Magnite (MGNI) insider sales made under a Rule 10b5-1 plan?

Yes. The footnote explains that the reported transactions were executed pursuant to a Rule 10b5-1 trading plan adopted by David Buonasera on September 11, 2025. Such plans pre-schedule trades, reducing the significance of short-term market timing decisions in these sales.

What type of transactions did Magnite (MGNI) report for its CTO?

The Form 4 reports open-market sales of Magnite Common Stock by CTO David Buonasera, coded as transaction type “S”. These are non-derivative transactions, meaning they involve direct share sales rather than option exercises, conversions, gifts, or tax-withholding related dispositions.

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Accepted by SEC EDGAR 06/17/2026 - 06:45 PM EDT 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).

X

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)
06/15/2026

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	06/15/2026		S(1)		1,057	D	$17	291,727	D
Common Stock	06/16/2026		S(1)		11,233	D	$18	280,494	D
Common Stock	06/17/2026		S(1)		1,409	D	$19	279,085	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. The reported transaction was effected pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on September 11, 2025.

	/s/ Aaron Saltz, attorney-in-fact	06/17/2026
	** 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)