Opera has released an update for its web browser for Windows that plugs several serious security holes.

The Opera 8.01 update was unveiled on Thursday, two months after the release of version 8 of the browser. Earlier last week the Norwegian software company also started shipping its latest version for Mac OS X.

The makers of the browser boast that the software has the best security track record in the industry.

However, some of the patched vulnerabilities put users at risk of spoofing and cross site scripting attacks, according to security firm Secunia which uncovered five of the flaws. The company gave a security ranking of 'moderately critical' to two of the flaws.

Spoofing cloaks the URL in the browser's address bar, allowing hackers to present the users with a website that appears legitimate but actually steals login names, passwords and other confidential information.

Cross site scripting is a technique that lets a hacker hijack a user's online identity through the use of HTML or Java scripts, allowing control of a session on an online bulletin board, for example, or the theft of user names and passwords.

In addition to the security fixes, the Opera 8.01 update features revisions in the user interface and functionality improvements, including the option to import sent emails to the browser's email application.

The Opera browser competes with Internet Explorer and Firefox, and has an estimated market share of around one per cent.