THURMOND MARK C. (Co-Chief Executive Officer) sold 21.8% of their position (28.50K shares) of TENABLE HOLDINGS, INC. on the open market

Open‑market sale worth $862.1K — a significant reduction. Review remaining holdings and any 10b5‑1 plan disclosures.

S · 1 sale

THURMOND MARK C.

Filed: 8/26/2025ACC: 0001660280-25-000104

InsiderTHURMOND MARK C.CIK 1651579

→

IssuerTENABLE HOLDINGS, INC.CIK 1660280

DirectorOfficer· Co-Chief Executive Officer

Since Feb 2026

-28.50K

Net shares

Net seller

$862.1K

Total sold

Open market trades

0B · 1S

Total transactions

63.31K acquired · 91.81K disposed

Non-Derivative Transactions8

Common Stock

Direct

M · Option Exercise

+1.16K

Price / share

—

Trade value

—

% of position

1.6%

8/22/2025

72.73K→73.89K

Common Stock

Direct

M · Option Exercise

+2.27K

Price / share

—

Trade value

—

% of position

3.1%

8/22/2025

73.89K→76.16K

Common Stock

Direct

M · Option Exercise

+3.71K

Price / share

—

Trade value

—

% of position

4.9%

8/22/2025

76.16K→79.87K

Common Stock

Direct

M · Option Exercise

+46.59K

Price / share

—

Trade value

—

% of position

58.3%

8/22/2025

79.87K→126.45K

Common Stock

Direct

M · Option Exercise

+4.37K

Price / share

—

Trade value

—

% of position

3.5%

8/22/2025

126.45K→130.82K

Common Stock

Direct

S · Sale

−28.50K

Price / share

$30.25

Trade value

$862.13K

% of position

21.8%

8/25/2025

130.82K→102.32K

Common Stock

Direct

M · Option Exercise

+1.36K

Price / share

—

Trade value

—

% of position

1.3%

8/25/2025

102.32K→103.69K

Common Stock

Direct

M · Option Exercise

+3.86K

Price / share

—

Trade value

—

% of position

3.7%

8/25/2025

103.69K→107.54K

Total

Net shares

+34.81K

Net value

-$862.13K

Security	Date	Type	Shares	Price / Share	Trade Value	% of Position	Held Before	Held After
Common Stock Direct	8/22/2025	M · Option Exercise	+1.16K	—	—	1.6%	72.73K	73.89K
Common Stock Direct	8/22/2025	M · Option Exercise	+2.27K	—	—	3.1%	73.89K	76.16K
Common Stock Direct	8/22/2025	M · Option Exercise	+3.71K	—	—	4.9%	76.16K	79.87K
Common Stock Direct	8/22/2025	M · Option Exercise	+46.59K	—	—	58.3%	79.87K	126.45K
Common Stock Direct	8/22/2025	M · Option Exercise	+4.37K	—	—	3.5%	126.45K	130.82K
Common Stock Direct	8/25/2025	S · Sale	−28.50K	$30.25	$862.13K	21.8%	130.82K	102.32K
Common Stock Direct	8/25/2025	M · Option Exercise	+1.36K	—	—	1.3%	102.32K	103.69K
Common Stock Direct	8/25/2025	M · Option Exercise	+3.86K	—	—	3.7%	103.69K	107.54K
Total			+34.81K		-$862.13K

Derivative Transactions7

Performance Restricted Stock Units

Direct

M · Option Exercise

Converts to

Common Stock

1.16K shares

−1.16K

Strike price

Held after

6.98K

Exercisable

—

8/22/2025

Performance Restricted Stock Units

Direct

M · Option Exercise

Converts to

Common Stock

2.27K shares

−2.27K

Strike price

Held after

22.67K

Exercisable

—

8/22/2025

Restricted Stock Units

Direct

M · Option Exercise

Converts to

Common Stock

3.71K shares

−3.71K

Strike price

Held after

22.28K

Exercisable

—

8/22/2025

Restricted Stock Units

Direct

M · Option Exercise

Converts to

Common Stock

46.59K shares

−46.59K

Strike price

Held after

139.76K

Exercisable

—

8/22/2025

Restricted Stock Units

Direct

M · Option Exercise

Converts to

Common Stock

4.37K shares

−4.37K

Strike price

Held after

43.68K

Exercisable

—

8/22/2025

Performance Restricted Stock Units

Direct

M · Option Exercise

Converts to

Common Stock

1.36K shares

−1.36K

Strike price

Held after

2.73K

Exercisable

—

8/25/2025

Restricted Stock Units

Direct

M · Option Exercise

Converts to

Common Stock

3.86K shares

−3.86K

Strike price

Held after

7.71K

Exercisable

—

8/25/2025

Security	Converts To	Date	Type	Shares	Exercisable	Held After
Performance Restricted Stock Units Direct	Common Stock1.16K shares	8/22/2025	M · Option Exercise	−1.16K	—	6.98K
Performance Restricted Stock Units Direct	Common Stock2.27K shares	8/22/2025	M · Option Exercise	−2.27K	—	22.67K
Restricted Stock Units Direct	Common Stock3.71K shares	8/22/2025	M · Option Exercise	−3.71K	—	22.28K
Restricted Stock Units Direct	Common Stock46.59K shares	8/22/2025	M · Option Exercise	−46.59K	—	139.76K
Restricted Stock Units Direct	Common Stock4.37K shares	8/22/2025	M · Option Exercise	−4.37K	—	43.68K
Performance Restricted Stock Units Direct	Common Stock1.36K shares	8/25/2025	M · Option Exercise	−1.36K	—	2.73K
Restricted Stock Units Direct	Common Stock3.86K shares	8/25/2025	M · Option Exercise	−3.86K	—	7.71K