We've had a half a dozen cases now of people editing content in different Craft 2.6 sites taking down our webservers.
- One staff member here editing a basic entry in the CMS has taken down a large cloud server multiple times over the past couple of months.
- A group of 20~ students uploading some basic projects in the CMS took down a different quad core webserver with 12GB of RAM and spiked the load to 250 - again multiple times.
I have little info to go off at this stage but I do know the load was caused by post requests made by php from the CMS. Front end traffic isn't the issue.
I'm nervous enough about this at the moment that the latest craft site I launched is on its own VPS to keep it away from other sites.
Happy to provide login/server deets to any of the Craft guys if they're curious, or if there's any more info people want, please let me know.