Next time you decide to buy some food from Amazon, first check if it's from a third-party vendor, then check the reviews to see if they've been shipping expired products, and finally, cross your fingers.

As CNBC reports, Amazon's open marketplace for third-party vendors has resulted in food and drink being sold that's not fit for consumption. How bad of a problem is it? Looking at Amazon's 100 best-selling food products alone, CNBC discovered 40 percent of sellers had "more than five complaints about expired goods."

The products complained about include baby formula and baby food, beef jerky, coffee creamer, granola bars, and specific brands such as Teavana, which Starbucks shutdown back in 2017. Customers receiving these goods complains of chemical or rancid smells, creamers when opened are curdled, chips are stale, beef jerky covered in mold, bottles of water refilled with tap water, and expiry dates on packaging from a year ago.

Amazon has clear policies in place for the sale of topical and consumable products. Products for regular application or consumption must have a minimum shelf life of 90 days, but the shelf life must also take into account the intended usage. For example, purchasing a pack of 180 one-a-day supplements must have a shelf life of at least 180 days + 90 days to comply with Amazon's policy.

Clearly the rules are not being followed by some sellers and the scale of the problem calls into question Amazon's policing of the marketplace. Thomas Gremillion, director of food policy at advocacy group Consumer Federation of America, commented, "There's no indication of how well that policy is enforced ... Some sellers could be making a business decision to sell expired products and let Amazon catch some of it and toss it out and persist."

Amazon has apparently taken "corrective action" regarding all expired food products CNBC brought to its attention, but also said that "they were isolated incidents that didn't require enforcement action against the sellers or removal of any products." Amazon has also since stated that, "For all of these ASINs, our systems detected and took appropriate actions at the time feedback was left."

An Amazon spokesperson commenting on how it monitored consumable product sales said, "We work hard to make sure customers receive high-quality products when they order from our store ... We have robust processes in place to ensure customers receive products with sufficient shelf life. If customers have concerns about items they've purchased, we encourage them to contact our Customer Service directly and work with us so we can investigate and take appropriate action"

The full extent of the expired food problem isn't known due to the way in which Amazon handles bad seller feedback regarding products shipped from an Amazon warehouse. Amazon will remove such feedback from a seller's profile if it believes the seller is not at fault and instead state it is taking "responsibility for this fulfillment experience." The knock-on effect of this being some percentage of expired food feedback may not be present on the site. Amazon does not remove customer reviews, though, and therefore they provide the best guide as to which sellers are breaking Amazon's seller rules.

Amazon is in danger of having its trust called into question over that most important of product categories: food. Considering the company owns Whole Foods and is continuing to introduce Amazon Go stores, the last thing it needs is an association with expired food.

Editor's Note: This story was updated at 11:30am ET with further details provided by an Amazon spokesperson.