Shares of VeriSign Inc., the main manager of the Internet-address database, plunged Friday after an extension of the contract letting the company to control Web sites ending in .com limited price increases.

In early New York trading, the shares were down 15 percent at $33.50. Through Thursday, the stock had advanced 10 percent this year.

The U.S. Department of Commerce approved a contract extension through Nov. 30, 2018 that lets VeriSign continue current pricing of $7.85 per domain name registration, the Reston, Virginia-based company said in a statement. VeriSign no longer has the right to four price increases of as much as 7 percent over the term of the contract, an option that was included in the previous accord.

VeriSign also works with others that sell .com addresses. Those companies pay VeriSign for the service that connects words to each correct Internet address.