How can I find conflicting keyboard shortcuts? I'm on Yosemite 10.10.4, using Safari 8.0.7.

When I press ⌘ + Shift + 7 Safari doesn't show all tabs, as it's supposed to be, but presents me with the crosshair you get when you would otherwise press ⌘ + Shift + 4.

When I press ⌘ + Shift + 4, I also get the crosshair.
Pressing ⌘ + Shift + 7 outside of Safari also gives me the crosshair.

I already checked all shortcuts defined under "System Preferences > Keyboard > Shortcuts" and I also used the apps CheatSheet and KeyCue to display shortcuts, but they only show ⌘ + Shift + 7 for "Show all tabs" in Safari and ⌘ + Shift + 4 for taking selected screenshots.

How can I find out, where the conflicting key bind is coming from? 

This behavior started a few days ago, but I can't seem to recall any specific changes or app installations, If there even were any...
I actually found the culprit...

In order to find the error I tried several other numbers with ⌘ + Shift and found ⌘ + Shift + 6 triggering a screen recording interface I hadn't seen before.

Opening this interfaces options I found it originated from CloudApp and there in CloudApps "Keyboard Shortcuts" I found it (see image).



CloudApp must have integrated the shortcut with it's recent update.

I removed the shortcut and now Safari is working again as it should :)