Language: Go
Label: vulnerable
CWE: CWE-287 \u2014 Improper Authentication
When an actor claims to have a given identity, the product does not prove or insufficiently proves that the claim is correct.

Code:
func (m mockAuth) AuthPlain(username, _ string) ([]string, error) {
	ids, ok := m.db[username]
	if !ok {
		return nil, errors.New("invalid creds")
	}
	return ids, nil
}