There are allegations that Israel is maintaining spy drones in Azerbaijan. Iran accuses Israel of keeping several huge Eitan drones on Azeri territory to spy on Iran. Relations between Israel and Azerbaijan have warmed in recent years, even as Israeli relations with nearby Georgia have cooled.
Iran has long viewed the Caucausus republics as being a stepping stone for Israel to attack Iran, at a time when Israeli aircraft would have difficulty attacking Iran directly due in part to the distance, and to the hostile territory between Israel and Iran.
In addition to the 3 or so Israeli controlled Eitan drones in Azerbaijan, the Azeris themselves are known to have at least ten Hermes 450 drones, and some smaller Searcher drones. Iran accuses Azerbaijan of spying over the border area of Karabakh. Drones flown over border areas can collect information from hundreds of miles across the frontier.
Warm relations between Israel and Georgia blew up a few years ago, after the Georgians used weapons acquired from Israel to confront Russia over territorial issues. Russia then forced Israel to abandon the Georgian arms deal, or face increased Russian arms sales to Iran. In the aftermath of the squelched arms deal Israeli arms companies sued the Georgian government over aspects of the broken contract. Wikileaks exposed documents that seemed to imply that Israel had supplied codes to Russia for Georgian drones, in return for Russia supplying codes for weapons owned by Iran.
Since then the Israeli government has pursued relations with the autocratic governnment of nearby Azerbaijan, including making large arms sales. Azerbaijan has a long border with Iran, which has many Azeri speakers in neighbouring provinces.