Copy machines have a relatively simple, single task so it's generally accepted that they'll function without issue and maintain 100 percent accuracy. Unfortunately, some owners of select Xerox products are experiencing a problem that goes against both of those expectations. Numbers in scanned documents are being swapped for erroneous digits, and unless you're looking closely at your copies, the issue could easily go unnoticed — but resulting headaches could be massive. "The scanned images look correct at first glance, even though numbers may actually be incorrect," writes David Kriesel, who uncovered the worrying bug last week while scanning construction documents. Numbers were randomly being altered, with 6 and 8 proving especially susceptible.

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It's not hard to come up with potential consequences for those affected: important business invoices could be thrown off, construction projects could be squandered, and so on. Kriesel says Xerox was unaware of the threat when he alerted the company last week, but it's already come forward with an explanation. Just as suspected, the underlying compression technology used by the machines is to blame. "The Xerox design utilizes the recognized industry standard JBIG2 compressor which creates extremely small file sizes with good image quality, but with inherent tradeoffs under low resolution and quality settings," explains principal engineer Francis Tse.

Further, he points out that Xerox already advises customers of this possibility in its software, describing results from normal compression settings as "acceptable" while warning that "text quality degradation and character substitution errors may occur." The company says upping the quality level to "higher" should guarantee the copy accuracy its customers expect.