Investors often turn to the Nasdaq Composite to gauge the performance of the technology sector. It has been on a bumpy ride over the last couple of years: It plunged 33% in 2022 but staged a strong rally this year, recording a gain of 31% so far. 

The 2023 rally stalled in August, and the index continued to slide in September. Seasonal weakness is playing a role, as some Wall Street bankers and fund managers take time off during those two months, leaving fewer buyers to pounce on dips in the market. Plus, there is lingering concern about how rising interest rates might affect the growth of high-flying technology companies. 

Long-term investors should look at this recent weakness in the Nasdaq Composite as a likely buying opportunity. Seasonality is a temporary headwind, and some experts predict the U.S. Federal Reserve might start cutting interest rates in the middle of 2024.

Given this recent Nasdaq sell-off, investors might do well to swoop in and buy the following two stocks. 

1. Tenable: Set to benefit from trillions of dollars in cybersecurity spending

If there is one industry set to do well regardless of the broader stock market conditions, it's cybersecurity. Hackers and malicious actors are becoming more sophisticated in a corporate world dominated by cloud computing, where valuable data and applications are hosted online around the clock. Tenable (TENB -2.35%) is a leading provider of vulnerability management software, which is an increasingly important part of the cybersecurity stack. 

Tenable's Nessus platform actively scans devices, operating systems, and cloud networks for vulnerabilities. It has been downloaded more than 2 million times, and it's the most accurate in the cybersecurity industry because it generates the lowest rate of false positives (in other words, it rarely mistakes a benign issue for a real threat). Furthermore, Nessus can alert customers to over 79,000 common vulnerabilities and exposures, which is more than any of its competitors.

Tenable has leveraged that success to build a portfolio of industry-specific cybersecurity tools to protect customers everywhere from the cloud to the endpoint. It offers specialized solutions for automotive manufacturers, healthcare providers, and even retailers, because a one-size-fits-all approach to cybersecurity won't work in the modern business environment.

Plus, Tenable recently launched a new generative artificial intelligence (AI) tool called ExposureAI, which can help businesses better understand their risk profiles and security posture. Cybersecurity managers can prompt ExposureAI to immediately find potential vulnerabilities in their networks, empowering them to react before malicious actors can pounce.

Tenable has grown its revenue by a modest 18% in the first half of 2023. But in the second quarter (ended June 30), it increased its full-year forecast, which suggests conditions could improve in the coming months. Besides, Tenable continues to attract high-spending customers in droves; in Q2, there were 1,507 businesses spending a minimum of $100,000 on Tenable's software, which was a 26% jump versus the prior-year period.

Longer-term, research firm McKinsey & Company predicts cyberattacks will cause $10.5 trillion in damage per year by 2025. It says businesses need to spend up to $2 trillion annually to protect themselves, yet in 2022, they only spent about $168 billion. That's a gap Tenable can help fill, and with its stock down 6% during the recent Nasdaq sell-off, now might be a great time to buy. 

2. Workiva: Gearing up for a new, lucrative opportunity

Organizations are increasingly reliant on online, cloud-based applications, not to mention remote workforces. That's a headache if you're a manager tasked with monitoring the progress of employees who work across dozens of online apps and might never be present in the office. Workiva (WK 2.04%) is giving them the tools to deal with those challenges.

The company has developed a cloud platform that connects to dozens of third-party productivity applications, storage apps, and accounting applications. Some of them include Microsoft Excel, Alphabet's Google Drive, and Salesforce. From there, Workiva aggregates data from all of them into one dashboard, creating a single source of truth for managers.

With data all in one place, Workiva also provides hundreds of reporting templates to make lodging forms with regulators like the Securities and Exchange Commission -- or presenting information to executive teams -- far easier and faster for managers.

But Workiva is also expanding into new verticals, and one of its biggest opportunities going forward is environmental, social, and governance (ESG) reporting. Global governments continue to introduce new rules requiring companies to track their impact on the environment and communities in which they operate, in order to improve carbon emissions and promote diversity in the workplace. 

An estimate by consulting specialist PwC suggests the ESG reporting software market was worth $9.6 billion in the U.S. and Europe in 2021. But it could grow by 12% per year until 2026, taking its value to nearly $17 billion. Considering Workiva expects to generate $627 million in revenue for the full 2023 year across its entire business, this new vertical could pave the way for significant long-term growth.

Plus, there are 5,860 business clients using Workiva's platform and 272 of them are spending more than $300,000 per year. Not only is that Workiva's top-spending customer group, but it's also its fastest growing, and that might continue as more large organizations adopt ESG reporting tools.

Workiva stock is down marginally so far in September, but it's still trading 33% below its all-time high set during the tech frenzy of 2021. That's likely a long-term buying opportunity for investors given the company's prospects.