Foundry376 Mailspring up to 1.16.x Quick Preview innerHTML cross site scripting

Summaryinfo

A vulnerability was found in Foundry376 Mailspring up to 1.16.x. It has been declared as problematic. Affected is the function innerHTML of the component Quick Preview. The manipulation results in cross site scripting. This vulnerability is identified as CVE-2026-93405. The attack can be executed remotely. There is not any exploit available. It is recommended to upgrade the affected component.

Detailsinfo

A vulnerability classified as problematic has been found in Foundry376 Mailspring up to 1.16.x. Affected is the function innerHTML of the component Quick Preview. The manipulation with an unknown input leads to a cross site scripting vulnerability. CWE is classifying the issue as CWE-79. The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users. This is going to have an impact on integrity. CVE summarizes:

Mailspring is a fast, cross-platform, open-source email client. Prior to 1.17.0, attachment quick preview converts Markdown, DOCX, and XLSX attachments with Snarkdown, Mammoth, and SheetJS and inserts the resulting HTML into the preview document through innerHTML without sanitization. A remote sender can craft a supported attachment whose converted HTML executes script when a recipient opens quick preview. The preview renderer has no direct Node or Electron access, but injected script can reach the IPC surface exposed to the quick-preview renderer. This issue alone provides script execution in the preview renderer; separate path-traversal and renderer-controlled file-write vulnerabilities are required for the documented persistent code-execution chain. This issue is fixed in version 1.17.0.

The advisory is shared for download at github.com. This vulnerability is traded as CVE-2026-93405 since 09/17/2026. The exploitability is told to be easy. It is possible to launch the attack remotely. The exploitation doesn't require any form of authentication. Successful exploitation requires user interaction by the victim. There are known technical details, but no exploit is available. The MITRE ATT&CK project declares the attack technique as T1059.007.

Upgrading to version 1.17.0 eliminates this vulnerability.

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Productinfo

Vendor

• Foundry376

Name

• Mailspring

Version

• 1.0
• 1.1
• 1.2
• 1.3
• 1.4
• 1.5
• 1.6
• 1.7
• 1.8
• 1.9
• 1.10
• 1.11
• 1.12
• 1.13
• 1.14
• 1.15
• 1.16

Website

• Product: https://github.com/Foundry376/Mailspring/

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