Summary
FV Player for WordPress contains an arbitrary file upload vulnerability caused by inadequate file type validation and missing authorization checks during new player creation. An authenticated attacker with subscriber-level access or higher may be able to place executable content in the public uploads directory, potentially enabling remote code execution if a race condition is successfully exploited.
FV Player for WordPress contains an arbitrary file upload vulnerability caused by inadequate file type validation and missing authorization checks during new player creation. An authenticated attacker with subscriber-level access or higher may be able to place executable content in the public uploads directory, potentially enabling remote code execution if a race condition is successfully exploited.
Affected context
The vulnerability occurs in FV Player deployments where the plugin's check_mimetype
function processes attacker-controlled remote file content during player creation.
The risk is higher when low-privilege authenticated users can reach the affected
workflow, when uploaded files are stored in a web-accessible directory, and when
the hosting environment permits uploaded content to execute. Successful exploitation
also depends on winning a race condition before effective file validation completes.
The vulnerability occurs in FV Player deployments where the plugin's check_mimetype
function processes attacker-controlled remote file content during player creation.
The risk is higher when low-privilege authenticated users can reach the affected
workflow, when uploaded files are stored in a web-accessible directory, and when
the hosting environment permits uploaded content to execute. Successful exploitation
also depends on winning a race condition before effective file validation completes.
Exploit preconditions
- Attack surface: WordPress plugin functionality for creating new players
- Required access: An authenticated account with subscriber-level access or higher
- Trigger point: Processing of attacker-supplied remote file content by
check_mimetype - Additional condition: A race condition must be successfully exploited
- Why exploitation is possible: File content may be written to the public uploads
directory before MIME and extension checks are applied, while the player-creation
workflow lacks an effective capability check
- Attack surface: WordPress plugin functionality for creating new players
- Required access: An authenticated account with subscriber-level access or higher
- Trigger point: Processing of attacker-supplied remote file content by
check_mimetype - Additional condition: A race condition must be successfully exploited
- Why exploitation is possible: File content may be written to the public uploads
directory before MIME and extension checks are applied, while the player-creation
workflow lacks an effective capability check
Why this happens
The underlying bug is an arbitrary file upload condition mapped to CWE-434: Unrestricted Upload of File with Dangerous Type. The application stores
attacker-controlled content in a web-accessible location before completing reliable
type validation, allowing validation order and timing to become security-critical.
The affected workflow also fails to enforce authorization for new player creation,
broadening the set of users who can reach the upload behavior. If the resulting file
is executable in the hosting environment, uploaded content may be interpreted as
server-side code.
The underlying bug is an arbitrary file upload condition mapped to CWE-434: Unrestricted Upload of File with Dangerous Type. The application stores
attacker-controlled content in a web-accessible location before completing reliable
type validation, allowing validation order and timing to become security-critical.
The affected workflow also fails to enforce authorization for new player creation,
broadening the set of users who can reach the upload behavior. If the resulting file
is executable in the hosting environment, uploaded content may be interpreted as
server-side code.
Potential impact
- An attacker may upload files containing executable content
- The web server may execute an uploaded file under suitable hosting conditions
- Application data and WordPress content could be modified or exposed
- Server-side credentials or connected services could be placed at risk
- The compromised site could be used for persistence, malware distribution, or lateral movement
- An attacker may upload files containing executable content
- The web server may execute an uploaded file under suitable hosting conditions
- Application data and WordPress content could be modified or exposed
- Server-side credentials or connected services could be placed at risk
- The compromised site could be used for persistence, malware distribution, or lateral movement
General mitigation guidance
Mitigation generally focuses on enforcing authorization and treating every uploaded
object as untrusted.
Common defensive patterns include:
- Require an explicit capability appropriate to player creation and file upload
- Validate file content, filename, extension, and declared MIME type before writing it
- Use an allowlist of non-executable formats rather than blocklists
- Avoid fetching remote content directly into public upload paths
- Store uploads outside executable web roots where practical
- Disable script execution in upload directories
- Use randomized server-side filenames and restrict file permissions
- Apply size, redirect, and network policies to remote file retrieval
- Run WordPress and its hosting components with least privilege
- Preserve atomic validation and storage behavior so incomplete checks cannot expose files
Mitigation generally focuses on enforcing authorization and treating every uploaded
object as untrusted.
Common defensive patterns include:
- Require an explicit capability appropriate to player creation and file upload
- Validate file content, filename, extension, and declared MIME type before writing it
- Use an allowlist of non-executable formats rather than blocklists
- Avoid fetching remote content directly into public upload paths
- Store uploads outside executable web roots where practical
- Disable script execution in upload directories
- Use randomized server-side filenames and restrict file permissions
- Apply size, redirect, and network policies to remote file retrieval
- Run WordPress and its hosting components with least privilege
- Preserve atomic validation and storage behavior so incomplete checks cannot expose files
How teams detect issues like this
Detection approaches may include:
- Static analysis for file writes that occur before MIME, extension, and content validation
- Review of upload handlers for missing capability or nonce checks
- Code review signals involving remote URL retrieval followed by writes to public directories
- Tests that submit mismatched, polyglot, and executable-looking file content
- Web-server monitoring for unusual new files or script requests under upload paths
- Policy enforcement that prohibits executable file types and script execution in media directories
- Automated security scanning and pull-request review tools to identify upload and authorization flaws
Detection approaches may include:
- Static analysis for file writes that occur before MIME, extension, and content validation
- Review of upload handlers for missing capability or nonce checks
- Code review signals involving remote URL retrieval followed by writes to public directories
- Tests that submit mismatched, polyglot, and executable-looking file content
- Web-server monitoring for unusual new files or script requests under upload paths
- Policy enforcement that prohibits executable file types and script execution in media directories
- Automated security scanning and pull-request review tools to identify upload and authorization flaws
