Summary
Legcord contains a path traversal vulnerability in theme-related IPC handlers that do not sufficiently validate theme identifiers. If script executes in the Discord origin, such as through an XSS condition, it may escape the intended themes directory to write files, delete directories, or launch local executables.
Legcord contains a path traversal vulnerability in theme-related IPC handlers that do not sufficiently validate theme identifiers. If script executes in the Discord origin, such as through an XSS condition, it may escape the intended themes directory to write files, delete directories, or launch local executables.
Affected context
The vulnerability occurs in Legcord's theme IPC functionality when theme identifiers are derived from content associated with the Discord page and are used in filesystem operations without adequate path confinement. Exploitation depends on script execution in the Discord origin and access to the affected theme operations, including installation, uninstallation, or folder handling.
The vulnerability occurs in Legcord's theme IPC functionality when theme identifiers are derived from content associated with the Discord page and are used in filesystem operations without adequate path confinement. Exploitation depends on script execution in the Discord origin and access to the affected theme operations, including installation, uninstallation, or folder handling.
Exploit preconditions
- Attack surface: Legcord theme IPC handlers, including
themes.folder,themes.uninstall, andthemes.install - Required access: Ability to execute script within the Discord origin, potentially through an XSS condition
- Trigger point: Processing a user-influenced theme identifier during a filesystem operation
- Why exploitation is possible: The identifier is not reliably constrained to the intended themes directory, allowing filesystem paths outside that directory to be selected
- Attack surface: Legcord theme IPC handlers, including
themes.folder,themes.uninstall, andthemes.install - Required access: Ability to execute script within the Discord origin, potentially through an XSS condition
- Trigger point: Processing a user-influenced theme identifier during a filesystem operation
- Why exploitation is possible: The identifier is not reliably constrained to the intended themes directory, allowing filesystem paths outside that directory to be selected
Why this happens
The underlying bug is improper neutralization of path elements in externally influenced input. Theme identifiers are used to construct filesystem paths without sufficient canonicalization, validation, or containment checks, allowing traversal outside the trusted themes directory. This behavior maps to CWE-22: Improper Limitation of a Pathname to a Restricted Directory, commonly known as path traversal.
The underlying bug is improper neutralization of path elements in externally influenced input. Theme identifiers are used to construct filesystem paths without sufficient canonicalization, validation, or containment checks, allowing traversal outside the trusted themes directory. This behavior maps to CWE-22: Improper Limitation of a Pathname to a Restricted Directory, commonly known as path traversal.
Potential impact
- An attacker may write files outside the themes directory
- An attacker could recursively delete accessible directories or files
- Local executables may be launched through unsafe filesystem or integration behavior
- User data, application integrity, or system availability could be affected
- The desktop application may be used as a bridge from web-origin script to local resources
- An attacker may write files outside the themes directory
- An attacker could recursively delete accessible directories or files
- Local executables may be launched through unsafe filesystem or integration behavior
- User data, application integrity, or system availability could be affected
- The desktop application may be used as a bridge from web-origin script to local resources
General mitigation guidance
Mitigation generally focuses on enforcing a strong boundary between web-origin input and local filesystem operations.
Common defensive patterns include:
- Treating theme identifiers as opaque names rather than filesystem paths
- Allowlisting permitted characters and rejecting traversal indicators or path separators
- Resolving candidate paths canonically and confirming they remain within the designated themes directory
- Using fixed internal identifiers instead of directly incorporating user-controlled values into paths
- Separating privileged filesystem actions from web-origin IPC requests
- Requiring explicit authorization and applying least privilege to local operations
- Restricting executable launching and using safe-by-default IPC contracts
Mitigation generally focuses on enforcing a strong boundary between web-origin input and local filesystem operations.
Common defensive patterns include:
- Treating theme identifiers as opaque names rather than filesystem paths
- Allowlisting permitted characters and rejecting traversal indicators or path separators
- Resolving candidate paths canonically and confirming they remain within the designated themes directory
- Using fixed internal identifiers instead of directly incorporating user-controlled values into paths
- Separating privileged filesystem actions from web-origin IPC requests
- Requiring explicit authorization and applying least privilege to local operations
- Restricting executable launching and using safe-by-default IPC contracts
How teams detect issues like this
Organizations can look for path traversal risks through:
- Static analysis of path joins, normalization routines, and filesystem APIs receiving IPC or web-origin data
- Code review checks for missing canonical-path containment validation
- Review of IPC handlers that expose file creation, deletion, directory access, or process-launching behavior
- Tests using traversal-like and encoded path values to verify rejection and directory confinement
- Runtime policy monitoring for unexpected writes, deletions, or process launches by the desktop application
- Automated security review tools that flag untrusted input flowing into filesystem operations
Organizations can look for path traversal risks through:
- Static analysis of path joins, normalization routines, and filesystem APIs receiving IPC or web-origin data
- Code review checks for missing canonical-path containment validation
- Review of IPC handlers that expose file creation, deletion, directory access, or process-launching behavior
- Tests using traversal-like and encoded path values to verify rejection and directory confinement
- Runtime policy monitoring for unexpected writes, deletions, or process launches by the desktop application
- Automated security review tools that flag untrusted input flowing into filesystem operations
