October conjures visions of haunted houses, ghostly apparitions, and leering jack-o'-lanterns. It is a month for scary things. And for many investors, the stock market crash that has unfolded over the past year certainly qualifies as scary. The S&P 500 is down 24% from its high, and the Nasdaq Composite is down 33%, putting both indexes in the jaws of a bear market.

Fortunately, there is a silver lining to the current downturn. High-quality companies like Shopify (SHOP -2.68%) and PayPal Holdings (PYPL -1.07%) have seen their stock prices fall into bargain territory, creating an excellent buying opportunity for patient investors.

Here's what you should know about these two growth stocks.

1. Shopify: The leading e-commerce software platform

Shopify is the operating system behind more than 2 million businesses. Its software helps merchants manage sales across multiple channels, including brick-and-mortar shops, online marketplaces, and direct-to-consumer websites. Shopify supplements its software with adjacent services like payment processing, discounted shipping, and financing. Few (if any) other vendors offer such a comprehensive solution.

Not surprisingly, Shopify is the most popular e-commerce software on the market, according to G2 Grid, and Shopify Plus, its commerce platform for larger companies, ranks as the second-most-popular product. In fact, over 14,000 enterprises currently use Shopify Plus, and the company is working to accelerate its momentum in that vertical. For instance, it recently debuted artificial intelligence-powered marketing software for Plus merchants, and it enhanced its business-to-business (B2B) commerce tools.

Like many retailers, Shopify has struggled throughout the year. High inflation has dampened consumer demand for discretionary items, and online shopping has naturally decelerated as the social impacts of the pandemic have faded. That said, Shopify continued to gain market share (both online and offline) in U.S. retail in the first and second quarters of 2022, and it still delivered modest financial results over the past year. Revenue climbed 30% to $5 billion, and while cash from operations fell 77% to $125 million, a positive number suggests that Shopify can continue to grow its business without issuing debt or equity.

Things may get worse in the near term if the macroeconomic environment continues to deteriorate, but patient investors still have good reason to be bullish. Shopify has a strong position in a massive market: eMarketer says retail e-commerce sales (i.e., business to consumer) will grow at 10% per year to reach $7.4 trillion by 2025, and Grand View Research estimates business-to-business e-commerce sales will grow at 20% per year to surpass $33 trillion by 2030.

Moreover, Shopify is working to strengthen its position through geographic expansion and product innovation. It recently launched point-of-sale hardware in Italy and Singapore, bringing the total to 13 countries; it also debuted payment processing services in France, bringing the total to 18 countries. Better yet, Shopify is building a fulfillment network across the U.S. to simplify logistics for merchants and accelerate delivery times for buyers. CFO Amy Shapero said on the Q1 earnings call in May that project will reach scale "toward the back half of 2023 and into 2024."

On that note, shares currently trade at an inexpensive 6.8 times sales -- the cheapest valuation in the last five years. That makes this growth stock a screaming buy.

2. PayPal: The leading digital wallet in North America and Europe

PayPal is the most accepted digital wallet in North America and Europe, and it was the most downloaded mobile finance app worldwide in the first half of 2022, according to Apptopia. That success stems from its trusted brand, its reliable platform, and its ability to engage both buyers and sellers with its two-sided payments network.

In other words, unlike traditional payment processors, PayPal often has data from both sides of a transaction. That gives the company an edge in identifying fraud. PayPal can also use that data to drive sales for merchants by surfacing relevant shopping deals for consumers who use its digital wallet. The company plans to lean into that competitive advantage in the second half of the year by redesigning its digital wallet's shopping hub.

PayPal's financial performance has been somewhat muted of late, due in part to eBay's migration away from the platform. But management says the eBay impact will be minimal in the second half of year, and cost-cutting measures should drive operating margin expansion in 2023. That said, PayPal still turned in decent results over the past year. Revenue climbed 11% to $26.4 billion and free cash flow rose 8% to $5.2 billion.

Investors have good reason to believe PayPal can reaccelerate growth. The company puts its addressable market at $110 trillion, and secular trends like online shopping and digital wallet adoption should be powerful catalysts. In fact, digital wallets are expected to take share from cash and payment cards in North America and Europe in the coming years, in both physical and digital settings, according to data from Worldpay.

Currently, shares trade at 3.8 times sales -- an absolute bargain compared to the three-year average of 8.7 times sales -- that's why patient investors should pile into this growth stock in October.