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 (fsys MkdirFsImpl) OpenAtEnd(name string) (fs.File, error) {
	file, err := os.OpenFile(fsys.dir+"/"+name, os.O_CREATE|os.O_RDWR, 0644)

	if err != nil {
		return nil, err
	}

	_, err = file.Seek(0, os.SEEK_END)
	if err != nil {
		return nil, err
	}

	return file, nil
}