A security researcher said he has discovered a vulnerability in Google Docs that mysteriously allows private documents to appear in other users' accounts.

Tim Bass, a researcher posting Monday on the ISC(2) blog, wrote that when he recently was using his Google Docs account he found that it was listing documents as "owned" by him but that did not belong to him.

In his case, he discovered documents written in Thai. When Bass contacted the owner of those files, that person also mentioned that his account contained documents not owed by him or normally shared with him.

Bass said he suspects a JavaScript error in the way in which Google manages user sessions is to blame. A Google spokeswoman said Tuesday afternoon that the company was prepping a fix.

Google Docs is a web-based application that saves files not to a user's desktop -- as is the case with programs such as Microsoft Office -- but to Google servers so users can retrieve documents from anywhere using the internet.

"The bottom line is that the security breach is real and dangerous," Bass said. "Your Google Docs, and I suspect other Google applications that use the same session management code, are vulnerable. There may be an underlying XSS (cross-site scripting) vulnerability as well."

A Google spokeswoman could not immediately be reached for comment on Tuesday.