Skip to content
Threat Feed
medium threat exploited

Notepad++ Vulnerability in Version 8.9.3 and Prior

A vulnerability exists in Notepad++ version 8.9.3 and prior, prompting a security advisory and the release of version 8.9.4 to address the issue.

On April 26, 2026, Notepad++ released a security advisory to address a vulnerability affecting version 8.9.3 and prior. The advisory urges users and administrators to update to version 8.9.4. While the specific nature of the vulnerability is not detailed in the advisory, the update is considered necessary for maintaining system security. The advisory does not specify any active exploitation of the vulnerability, but users of affected versions should update promptly to mitigate potential risks.

Attack Chain

  1. Attacker identifies a vulnerable Notepad++ instance running version 8.9.3 or earlier.
  2. Attacker crafts a malicious file or input designed to exploit the undisclosed vulnerability.
  3. User opens the malicious file or interacts with the crafted input within Notepad++.
  4. The vulnerability is triggered, potentially leading to arbitrary code execution.
  5. Attacker gains control of the Notepad++ process.
  6. Attacker leverages the compromised Notepad++ process to escalate privileges.
  7. Attacker uses the escalated privileges to execute further malicious actions on the system.
  8. Attacker achieves their objective, such as data exfiltration or system compromise.

Impact

Successful exploitation of this vulnerability could allow an attacker to execute arbitrary code, potentially leading to sensitive data compromise, system takeover, or further malicious activities on the affected machine. The impact scope is limited to systems running vulnerable versions of Notepad++. The specific number of affected users is unknown.

Recommendation

  • Upgrade to Notepad++ version 8.9.4 or later as recommended in the Notepad++ release 8.9.4.
  • Monitor process execution for unusual or suspicious activity originating from Notepad++ using process creation logs.
  • Deploy the Sigma rule Detect Suspicious Notepad++ Child Processes to identify potentially malicious child processes spawned by Notepad++.

Detection coverage 2

Detect Suspicious Notepad++ Child Processes

high

Detects suspicious child processes spawned by Notepad++, which may indicate exploitation.

sigma tactics: execution techniques: T1059.001 sources: process_creation, windows

Detect Notepad++ Writing Executables

medium

Detects Notepad++ writing executable files, which may indicate malware creation or modification.

sigma tactics: defense_evasion techniques: T1027 sources: file_event, windows

Detection queries are available on the platform. Get full rules →