** Cybersecurity firm Castellum's shares CTM.A plunge as much as 20.3%; last down 13.6% at $1.02

** CTM late Sunday priced its public offering of 4.5 million units at $1 each for gross proceeds of $4.5 million

** Offering priced at 15.3% discount to stock's last close

** Each unit consists of one share and warrant

** Warrants can be immediately exercised at $1.08 per share and expire 60 days from the date of issuance

** Maxim Group was the sole placement agent for the offering

** CTM plans on using the proceeds for working capital and general purposes

** Stock down 49% YTD after 571% jump in 2024

(Reporting by Arasu Kannagi Basil in Bengaluru)

((ArasuKannagi.Basil@thomsonreuters.com))