From the USCIS Public Engagement Division:
If an H-1B, H-2A, or H-2B petitioner submits evidence establishing that the primary reason for failing to timely file an extension of stay or change of status request was due to the government shutdown, USCIS will consider the government shutdown as an extraordinary circumstance and excuse the late filing, if the petitioner meets all other applicable requirements.
For more information, please visit www.uscis.gov.