Mozilla slows Firefox 66 rollout to fix bug making Office 365 PowerPoint text vanish

Firefox 66's initial release made Microsoft's PowerPoint online useless for creating presentations.

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Firefox-maker Mozilla has put the brakes on the release of Firefox 66 after users discovered text would simply vanish after typing into PowerPoint on Office 365. 

For the second month in a row, Mozilla has stalled the rollout of its latest stable release of Firefox. Firefox 65 triggered insecure connection warnings for AVG and Avast antivirus users. 

The current pause on Firefox 66, spotted by Techdows, followed a report from a Firefox user who found that the browser caused some very odd behavior in Microsoft's online version of PowerPoint.  

"Try to type anything anywhere," the user explains. "Actual results: Text vanishes forever. Expected results: Text appears in box like normal."

Firefox developers have been able to reproduce the bug and admit that Office 365 PowerPoint has a vanishing text problem in Firefox 66 for Mac and Windows. 

"Text in boxes automatically vanishes after typing. You cannot add any text to text boxes," the official bug report explains. The issue affects titles and text boxes. 

So the developers decided, just a day after releasing Firefox 66, to throttle its availability. Firefox 66 brought Windows Hello support for passwordless sign-in and a block on auto-play videos with sound. 

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Firefox bug-fixer Dennis Schubert explains the problem and a potential fix. However, Firefox developers were concerned the fix could break other Office 365 apps. 

"I can reproduce the issue. PowerPoint itself seems to be a giant iFrame to powerpoint.officeapps.live.com for both the Free/Personal Office 365 (which runs under at onedrive.live.com) and the enterprise one (which seem to be subdomains of sharepoint.com)."

His suggested fix was changing the dom.keyboardevent.keypress.hack.use_legacy_keycode_and_charcode preference value to powerpoint.officeapps.live.com. 

But he added: "It may be wise to use *.officeapps.live.com, though, because other Office 365 apps might be broken in some way as well, and/or ping Microsoft to check if there are other domains as well."

The developers were yesterday looking to deliver a fix using Normandy, Mozilla's system for making changes to a preference value for a target group without actually deploying an update to Firefox. Developers can create a 'Normandy recipe' to ship to users. 

Firefox bug fixers shipped a temporary hot fix in the Normandy recipe id 721, which includes Schubert's suggested fix, so PowerPoint online should be behaving as normal now. 

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