static const char *cmd_hash_engine(cmd_parms *cmd, void *_dcfg, const char *p1)
{
    directory_config *dcfg = (directory_config *)_dcfg;
    if (dcfg == NULL) return NULL;

    if (strcasecmp(p1, "on") == 0)  {
        dcfg->hash_is_enabled = HASH_ENABLED;
        dcfg->hash_enforcement = HASH_ENABLED;
    }
    else if (strcasecmp(p1, "off") == 0)    {
        dcfg->hash_is_enabled = HASH_DISABLED;
        dcfg->hash_enforcement = HASH_DISABLED;
    }
    else return apr_psprintf(cmd->pool, "ModSecurity: Invalid value for SecRuleEngine: %s", p1);

    return NULL;
}
The software processes an XML document that can contain XML entities with URIs that resolve to documents outside of the intended sphere of control, causing the product to embed incorrect documents into its output.