diff --git a/openwpm/browser_manager.py b/openwpm/browser_manager.py
index 2d929a611..f7c81b7dc 100644
--- a/openwpm/browser_manager.py
+++ b/openwpm/browser_manager.py
@@ -131,6 +131,33 @@ def launch_browser_manager(self) -> bool:
 
             crash_recovery = True
 
+        # Create a unique temporary directory that we can delete
+        # when we shut down.  Note that this doesn't force anything to
+        # use `tmpdir`, it just makes it available.
+        if self.browser_params.tmpdir is not None:
+            self.logger.debug(
+                "BROWSER %i: leftover temp directory %s?  Deleting it."
+                % (self.browser_id, self.browser_params.tmpdir)
+            )
+            try:
+                shutil.rmtree(self.browser_params.tmpdir)
+            except Exception:
+                self.logger.debug(
+                    "BROWSER %i: error deleting %s"
+                    % (
+                        self.browser_id,
+                        self.browser_params.tmpdir,
+                    ),
+                    exc_info=True,
+                )
+        self.browser_params.tmpdir = Path(
+            tempfile.mkdtemp(prefix="openwpm_", dir=os.getenv("TMPDIR", default="/tmp"))
+        )
+        self.logger.debug(
+            "BROWSER %i: Using temp dir %s"
+            % (self.browser_id, self.browser_params.tmpdir)
+        )
+
         self.logger.info("BROWSER %i: Launching browser..." % self.browser_id)
         self.is_fresh = not crash_recovery
 
@@ -340,6 +367,34 @@ def close_browser_manager(self, force: bool = False) -> None:
             if not shutdown_complete:
                 self.kill_browser_manager()
 
+            # Delete the temporary directory used by geckodriver.
+            if self.browser_params.tmpdir is not None:
+                try:
+                    t1 = time.time()
+                    self.logger.debug(
+                        "BROWSER %i: deleting temp dir %s"
+                        % (self.browser_id, self.browser_params.tmpdir)
+                    )
+                    shutil.rmtree(self.browser_params.tmpdir)
+                    self.logger.debug(
+                        "BROWSER %i: completed deleting temp dir %s in %d seconds"
+                        % (
+                            self.browser_id,
+                            self.browser_params.tmpdir,
+                            time.time() - t1,
+                        )
+                    )
+                    self.browser_params.tmpdir = None
+                except Exception as e:
+                    self.logger.warn(
+                        "BROWSER %i: failed to delete temp dir %s"
+                        % (
+                            self.browser_id,
+                            self.browser_params.tmpdir,
+                        ),
+                        exc_info=True,
+                    )
+
     def execute_command_sequence(
         self,
         # Quoting to break cyclic import, see https://stackoverflow.com/a/39757388
diff --git a/openwpm/config.py b/openwpm/config.py
index 674d8dab6..e42824550 100644
--- a/openwpm/config.py
+++ b/openwpm/config.py
@@ -103,6 +103,7 @@ class BrowserParams(DataClassJsonMixin):
         default=Path(tempfile.gettempdir()),
         metadata=DCJConfig(encoder=path_to_str, decoder=str_to_path),
     )
+
     """
     The tmp_profile_dir defaults to the OS's temporary file folder (typically /tmp) and is where the generated 
     browser profiles and residual files are stored.
@@ -139,6 +140,18 @@ class BrowserParams(DataClassJsonMixin):
 
     """
 
+    tmpdir: Optional[Path] = field(
+        default=None,
+        metadata=DCJConfig(encoder=path_to_str, decoder=str_to_path),
+    )
+    """
+    The temporary directory used by `geckodriver`.  This is configured in
+    `BrowserManager.run` and then deleted when the browser is finished.  We do
+    this because it seems that `geckodriver` doesn't clean up its temporary
+    files (in particular, a copy of the extension XPI file), so we need to do
+    so ourselves.
+    """
+
     recovery_tar: Optional[Path] = None
     donottrack: bool = False
     tracking_protection: bool = False
diff --git a/openwpm/deploy_browsers/deploy_firefox.py b/openwpm/deploy_browsers/deploy_firefox.py
index c4797b794..b5c4a6e29 100755
--- a/openwpm/deploy_browsers/deploy_firefox.py
+++ b/openwpm/deploy_browsers/deploy_firefox.py
@@ -140,6 +140,14 @@ def deploy_firefox(
     # Launch the webdriver
     status_queue.put(("STATUS", "Launch Attempted", None))
 
+    # Use browser_params.tmpdir as the temporary directory.  This is so that
+    # geckodriver makes its copy of the extension XPI file in tmpdir, so
+    # we can delete it later and not have it left behind.  I make a shallow
+    # copy of `os.environ` because I'm a little nervous about modifying the
+    # OpenWPM process' environment.
+    env = os.environ.copy()
+    env["TMPDIR"] = str(browser_params.tmpdir)
+
     fo.binary_location = firefox_binary_path
     geckodriver_path = subprocess.check_output(
         "which geckodriver", encoding="utf-8", shell=True
@@ -149,6 +157,7 @@ def deploy_firefox(
         service=Service(
             executable_path=geckodriver_path,
             log_output=open(webdriver_interceptor.fifo, "w"),
+            env=env,
         ),
     )