Language: Go
Label: vulnerable
CWE: CWE-22 \u2014 Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')
The product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory.

Code:
func (file WritableFile) Write(data []byte) (int, error) {
	file.fsys[file.path].Data = data
	return len(data), nil
}