Fluid Attacks logo
Contact Us
Young hacker smiling
Zero false positives

Expert intelligence + effective automation

Contact logo Contact Us

R329. Keep client-side storage without sensitive data

This document contains the details of the security requirements related to the definition and management of sensitive data in the organization. This requirement establishes the importance of avoiding the storage of sensitive information in the localStorage.


Personal, sensitive and session data must not be stored in the client-side storage (localStorage, sessionStorage, cookies without security attributes, mobile device unencrypted storage, etc.).


Data placed in the localStorage persists after a session is closed; thus, any actor with access to the browser will be able to obtain it. Furthermore, data in the localStorage or in the sessionStorage is visible to scripts that are running on the browser, and these scripts could belong to malicious third-parties. Therefore, no sensitive or session information should be stored in the client-side storage.


  1. CWE-922: Insecure Storage of Sensitive Information The software stores sensitive information without properly limiting read or write access by unauthorized actors.

  2. Directive 2002/58/EC (amended by E-privacy Directive 2009/136/EC). Art. 4: Security of processing.(1a) The measures referred to in paragraph 1 shall at least protect personal data stored or transmitted against accidental or unlawful destruction, accidental loss or alteration, and unauthorized or unlawful storage, processing, access or disclosure.

  3. GDPR. Art. 5: Principles relating to processing of personal data.(1)(f). Personal data shall be processed in a manner that ensures appropriate security of the personal data, including protection against unauthorized or unlawful processing and against accidental loss, destruction or damage.

  4. GDPR. Recital 51: Protecting sensitive personal data. Personal data which are, by their nature, particularly sensitive in relation to fundamental rights and freedoms merit specific protection as the context of their processing could create significant risks to the fundamental rights and freedoms.

  5. OWASP-ASVS v4.0.1 V8.2 Client-side Data Protection.(8.2.2) Verify that data stored in client side storage (such as HTML5 local storage, session storage, IndexedDB, regular cookies or Flash cookies) does not contain sensitive data or PII.

Service status - Terms of Use