Opera has patched three bugs in its web browser, and taken a swipe at Firefox developer Mozilla for irresponsibly revealing one of them on the web before giving its competitor a chance to release a fix.

The Opera 9.26 update plugs three vulnerabilities, the most serious of which is rated "highly severe" as it could be used by attackers to dupe the browser into treating image-file comments as script. "This can cause the script to be run in the wrong security context," Opera's advisory read.

But it was another, less-dangerous bug that raised the ire of Claudio Santambrogio, Opera's quality assurance desktop test manager. In a post to a company blog last week, Santambrogio used the flaw to take Mozilla to task.

"Mozilla notified us of one security issue the day before they published their public advisory," said Santambrogio. "They did not wait for us to come back with an ETA for a fix. They kept their bug reports containing the details of the exploits closed to the public for a few days, and now opened most of them to everybody."

The bug, which was one of 11 that Mozilla patched earlier this month when it released Firefox 2.0.0.12, could let attackers spoof input fields. Mozilla said that the vulnerability could be used to dupe users into unwittingly uploading malicious code; Opera's advisory agreed.

Although Santambrogio claimed that Mozilla had opened the vulnerability's Bugzilla entry - and thus disclosed details of the bug before Opera was able to patch - the entry is currently locked. It is inaccessible even to users with a general Bugzilla account.

Santambrogio seemed to knock Mozilla for not abiding by the unwritten rule of 'responsible disclosure', which requires that researchers wait until vendors patch a bug before revealing details of the vulnerability. "Opera is as always committed to not only protecting its users, but to making the web a safe place. We believe in responsible [emphasis in original] disclosure of vulnerabilities affecting several vendors," he said.

Mozilla said it would not comment on the dustup.

Opera 9.26 can be downloaded from the company's website in versions for Windows, Mac OS X and Linux.