Logitech is encouraging users with their Unifying Receiver USB dongle to update to the latest firmware now and anticipate another firmware update in August to patch some security issues.
Logitech also says they will not be issuing patches for 2 other security issues that a researcher uncovered because they wouldn't be compatible some older, "legacy" Logitech keyboards and mice. They also claim that it would require special equipment and skills, as well as proximity to - or even physical access to - the target computer or device to exploit the 2 issues they won't be patching.
I believe that at least some Dell Unifying Receiver dongles were made by Logitech and they may be affected too. So at the least, update the dongle's firmware.
Read more from Logitech here and the comments from upset users too.... ;o))