• Guggenheim Securities analysts downgraded CrowdStrike stock, saying signings could be affected after Friday's widespread outage of Windows computers stemming from a faulty CrowdStrike software update.
• Over the weekend, people posted photos of Windows devices that still needed attention.

CrowdStrike shares slipped 13% during Monday's trading session, as the cybersecurity software company continued to help clients across industries recover from an outage that took millions of Microsoft Windows devices offline last week.

Early on Friday, the company issued a defective update to its Falcon vulnerability-protection software that caused PCs, computer servers in data centers and display screens to crash, resulting in grounded flights and canceled medical appointments. The incident ensnared 8.5 million Windows devices, less than 1% of the global total, Microsoft said.

IT staffers quickly worked to fix computers. Meanwhile, hackers sought to take advantage of the confusion by setting up malicious websites that appeared to offer software updates. CrowdStrike CEO George Kurtz addressed the situation on air with CNBC's Jim Cramer.

CrowdStrike shares fell 11% on Friday. But then, over the weekend, people shared photos on social media of Windows devices displaying the so-called "blue screen of death," a sign of computers in need of attention from administrators. CrowdStrike said on Sunday that it was testing a method that would fix affected machines more quickly.

Guggenheim Securities downgraded its rating on CrowdStrike shares to neutral from buy on Sunday. Analysts led by John DiFucci said the stock was still trading at "the highest multiple of recurring revenue across our entire software coverage."

It might take time for CrowdStrike to repair its image, and the fallout will probably hurt signings, the analysts wrote. Signings are an early estimate of contract value from new and existing customers that can give investors a sense of a company's potential for revenue generation.

"We still have the utmost respect for the leadership team at CrowdStrike and believe that the company will eventually become even stronger as a result of this incident, and if investors have a multi-year horizon, they can ride it out," they wrote. "However, we find it difficult to tell investors that they need to buy CRWD right now."

Goldman Sachs maintained their buy rating on CrowdStrike shares in a note issued early Monday. But analysts at the investment bank said they expected CrowdStrike's deals to take longer to close between the time of the outage and July 31 — the end date of the software company's fiscal second quarter.

"Our recent conversations reaffirm our view that there will likely be minimal share shifts in endpoint post this event — although we recognize that additional details in the postmortem will further inform this view," analysts led by Gabriela Borges wrote.

They pointed to a 2010 McAfee outage that caused computer crashes to give a sense of what came before last week's events.

"The revenue impact due to deferrals was about $6 million of deferred revenue not recognized from the balance sheet, and revenue was also negatively impacted by another approximately $14 million," then-CEO Dave DeWalt told analysts in July of that year on a conference call. Kurtz was McAfee's chief technology officer at the time.

Less than one month after the McAfee earnings call, Intel announced its intent to buy the antivirus company for $7.7 billion.

"This is an evolving situation," CrowdStrike said in a regulatory filing on Monday. "We continue to evaluate the impact of the event on our business and operations."

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