Fastly Inc. /zigman2/quotes/212251938/composite FSLY -0.82% shares dropped in the extended session Wednesday after the cloud-based online content services company identified video-sharing platform TiKTok as its largest customer following an earnings beat. Fastly shares fell 14% after hours, following a 6.3% decline in the regular session to close at $108.92 for a 443% year-to-date gain. In an interview with Barron's, Fastly Chief Executive Joshua Bixby said that TikTok was the company's single largest customer, accounting for 12% of revenue this past quarter. President Donald Trump has cited TiKTok as a national-security risk because of ownership by Chinese parent company ByteDance and has suggested the Treasury should get a cut of the purchase price should Microsoft Corp. /zigman2/quotes/207732364/composite MSFT +0.44% acquire it. The company reported a second-quarter loss of $14.5 million, or 14 cents a share, compared with a loss of $15.6 million, or 25 cents a share, in the year-ago period. Adjusted earnings were 2 cents a share. Revenue rose to $74.7 million from $46.2 million in the year-ago quarter. Analysts surveyed by FactSet had forecast a loss of a penny a share on revenue of $71.4 million. Fastly expects an adjusted loss of a penny a share to net income of a penny a share on revenue of $73.5 million to $75.5 million in the third quarter. Analysts had forecast a loss of 4 cents a share on revenue of $72 million.