update requirements for server (#2172)

backend/server/requirements-prepare.txt

@@ -1,2 +1,2 @@
-python-igraph
+python-igraph>=0.8
 louvain>=0.6

backend/server/requirements.txt

@@ -4,7 +4,7 @@ click>=7.1.2
 fastobo>=0.6.1
 Flask>=1.0.2
 Flask-Compress>=1.4.0
-Flask-Cors>=3.0.6
+Flask-Cors>=3.0.9  # CVE-2020-25032
 Flask-RESTful>=0.3.6
 flask-server-timing>=0.1.2
 flask-talisman>=0.7.0
@@ -13,12 +13,13 @@ flatten-dict>=0.2.0
 fsspec>=0.4.4,<0.8.0
 gunicorn>=20.0.4
 h5py<3.0.0 # h5py>=3.0.0 had a breaking change; there is a fix in anndata>=0.7.5
-numba>=0.49.1,<0.53.0
-numpy>=1.15.0
+jinja2>=2.11.3  # Flask sub-dependency. Added due to CVE-2020-28493
+numba>=0.51.2,<0.53.0
+numpy>=1.17.5
 packaging>=20.0
 pandas>=1.0,!=1.1  # pandas 1.1 breaks tests, https://github.com/pandas-dev/pandas/issues/35446
-PyYAML>=5.3
-scipy>=1.0
+PyYAML>=5.4  # CVE-2020-14343
+scipy>=1.4
 requests>=2.22.0
 s3fs==0.4.2
 scanpy==1.4.6 # Until we move to anndata 0.7.4 scanpy needs to be pinned here