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...