Barclays says investors should buy Poshmark, a leader in the fast-growing online second-hand apparel market that could see more than 40% upside from here. Analyst Trevor Young upgraded Poshmark to overweight from equal weight and raised Barclays' price target, citing Poshmark's "strong user base, sticky buyer behavior and social media-like engagement." The upgrade comes despite the fact, "POSH isn't out of the woods yet on navigating ad-targeting post IDFA [Identifier for Advertisers], and marketing continues to ramp as a percentage of revenue, pressuring EBITDA back into negative territory," Young wrote in a Monday note. "The CAC[cost of acquiring customers]/buyer flywheel is critical for these asset-light marketplaces," but Poshmark continues to offer "a critical mass of active buyers that's still growing, high engagement from the social/gamification aspects of the platform, secular tailwinds to secondhand, and opportunity to outperform as consumers trade-down in a softer macro," Young added. Poshmark, which is down roughly 30% this year and 60% off its 52-week high, struggled with Apple's recent privacy changes. Still, the business looks like it's poised to turn around. "Second-hand marketplaces are still comparatively small, but names like POSH have achieved critical mass, and to the extent they continue to expand categories, we see ample runway to tap into different demos," Young wrote. The analyst raised Poshmark's target price to $17 from $13. The new target implies 44% upside from Friday's close of $11.80. The stock jumped 5% in Monday premarket trading. —CNBC's Michael Bloom contributed to this report.