(Bloomberg) -- A popular category of carbon offsets held by a number of major publicly traded companies is significantly more prone to greenwashing than previously feared, according to a new investigation of the financial instruments.Most Read from BloombergCaesars Entertainment Paid Millions to Hackers in AttackByron Allen Makes $10 Billion Bid for ABC, Other Disney NetworksVideo-Game Company Unity Closes Offices Following Death ThreatWhen the Homeowners Association Comes for Your HomeDisney Ho