Investors shaken by the stock market's pullback in August should be on the alert for even steeper declines ahead for six stocks with a range of vulnerabilities, including PayPal Holdings Inc. (PYPL), Dropbox Inc. (DBX), Molson Coors Brewing Company (TAP), MSG Network Inc. (MSGN), Domino’s Pizza Inc. (DPZ), and Dish Network Corp. (DISH). They are especially prone to pullbacks as new global risks emerge, according to a detailed story in Barron’s.

One challenge facing these six stocks is stiffer competition, which includes: Dropbox’s storage service vs. rival offerings from cloud-based tech giants; Molson’s dwindling beer brands vs. the rise of hard seltzers and canned wine; Domino’s vs. the mass of new delivery services making every restaurant a potential threat; and PayPal vs. new competitors that operate on eBay Inc.'s (EBAY) platform. For its part, MSG Network's big challenge is loss of subscribers. And Dish Network may struggle since its plan to sell its wireless spectrum has fallen through following the approval of the T-Mobile–Sprint merger.

What it Means for Investors

While several of these stocks rose on Tuesday on news that the White House may delay tariffs on some products, the negative forces weighing on these stocks remain. Domino’s Pizza, for one, posted its slowest quarterly sales growth in almost seven years for the most recent quarter, and has been looking into ways it can reduce labor costs, such as through autonomous cars and more effective scheduling of its drivers during rush-times. But that won't slow competitive pressure from fast-expanding delivery rivals like GrubHub Inc. (GRUB), DoorDash Inc. and Uber Technologies Inc.’s (UBER) Uber Eats. These companies are forming partnerships with restaurants and making it easy for customers to order delivery from any restaurant, according to Barron’s

And PayPal's outlook has dimmed despite two robust years of growth. About 11% of PayPal’s revenue comes from the U.K., which could take a hit from Brexit, and stricter European customer-authentication regulations will also weigh on PayPal’s European business, according to Barron’s. The company recently lowered its full-year revenue guidance below analysts' estimates. The lowered guidance comes as its arrangement with eBay nears an end in 2020 and the online auctioneer and retailer seeks new partners.

Looking Ahead

CEOs at these companies must contend not only with the short-term upheaval of the latest global economic or political crises, but with imminent competitive threats to their revenue growth and livelihood. That makes it more likely than not that these stocks will underperform as investors shed the weakest assets from their portfolio.