Users who have the latest Flash plugin installed (which was automatically updated via the latest updates to both Chrome and Firefox this week) will see the following crash notification when trying to login into their vCenter server via the vSphere Web Client.
The issue (and workaround) is detailed in VMware KB 2151945. One workaround is to replace the newest version of the pepflashplayer.dll with the previous, 22.214.171.124 version. This may be found on the computer (older versions are sometimes retained), but it can also be downloaded from the VMware KB article. After replacing the DLL, restarting the Chrome or Firefox browser should do the trick and allow you to sign into the vSphere Web Client.
Consider the Security Implications
One caveat (and it’s an important one): Adobe released this new version of Shockwave Flash (126.96.36.199) to fix a zero-day vulnerability that existed in previous versions, including the version that you have to use for the workaround. The vulnerability is detailed here. So caution and discretion should be exercised when weighing vCenter access vs. security. But the above workaround will allow a person to log in and use vCenter. A safe suggestion would be to use a dedicated VM for accessing vCenter via the older Flash plugin, and ensure normal workstations are using the latest plugin to remain protected.
Adobe is aware of the issue and working on a fix, though it may not be published for a couple of weeks. In the interim, Adobe has suggested an alternative workaround in order to retain the security protections that 188.8.131.52 provides. Adobe has released a beta version of Flash Player 27 that both fixes the Web Client crashes and the security vulnerability. The beta version can be downloaded here. It is important to note that this is a beta version, and users should upgrade to the GA version as soon as it is available.