rpc: fix content-type header (#5661)

CHANGELOG_PENDING.md

@@ -9,8 +9,7 @@ Friendly reminder, we have a [bug bounty program](https://hackerone.com/tendermi
 ### BREAKING CHANGES
 
 - CLI/RPC/Config
-
-    - [config] \#5598 The `test_fuzz` and `test_fuzz_config` P2P settings have been removed. (@erikgrinaker)
+  - [config] \#5598 The `test_fuzz` and `test_fuzz_config` P2P settings have been removed. (@erikgrinaker)
 
 - Apps
 
@@ -31,5 +30,6 @@ Friendly reminder, we have a [bug bounty program](https://hackerone.com/tendermi
 
 ### BUG FIXES
 
+- [rpc] \#5660 Set `application/json` as the `Content-Type` header in RPC responses.
 - [types] \#5523 Change json naming of `PartSetHeader` within `BlockID` from `parts` to `part_set_header` (@marbar3778)
 - [privval] \#5638 Increase read/write timeout to 5s and calculate ping interval based on it (@JoeKash)

rpc/jsonrpc/client/http_json_client.go

@@ -151,10 +151,13 @@ func NewWithHTTPClient(remote string, client *http.Client) (*Client, error) {
 }
 
 // Call issues a POST HTTP request. Requests are JSON encoded. Content-Type:
-// text/json.
-func (c *Client) Call(ctx context.Context, method string,
-	params map[string]interface{}, result interface{}) (interface{}, error) {
-
+// application/json.
+func (c *Client) Call(
+	ctx context.Context,
+	method string,
+	params map[string]interface{},
+	result interface{},
+) (interface{}, error) {
 	id := c.nextRequestID()
 
 	request, err := types.MapToRequest(id, method, params)
@@ -172,14 +175,18 @@ func (c *Client) Call(ctx context.Context, method string,
 	if err != nil {
 		return nil, fmt.Errorf("request failed: %w", err)
 	}
-	httpRequest.Header.Set("Content-Type", "text/json")
+
+	httpRequest.Header.Set("Content-Type", "application/json")
+
 	if c.username != "" || c.password != "" {
 		httpRequest.SetBasicAuth(c.username, c.password)
 	}
+
 	httpResponse, err := c.client.Do(httpRequest)
 	if err != nil {
 		return nil, fmt.Errorf("post failed: %w", err)
 	}
+
 	defer httpResponse.Body.Close()
 
 	responseBytes, err := ioutil.ReadAll(httpResponse.Body)
@@ -216,14 +223,18 @@ func (c *Client) sendBatch(ctx context.Context, requests []*jsonRPCBufferedReque
 	if err != nil {
 		return nil, fmt.Errorf("new request: %w", err)
 	}
-	httpRequest.Header.Set("Content-Type", "text/json")
+
+	httpRequest.Header.Set("Content-Type", "application/json")
+
 	if c.username != "" || c.password != "" {
 		httpRequest.SetBasicAuth(c.username, c.password)
 	}
+
 	httpResponse, err := c.client.Do(httpRequest)
 	if err != nil {
 		return nil, fmt.Errorf("post: %w", err)
 	}
+
 	defer httpResponse.Body.Close()
 
 	responseBytes, err := ioutil.ReadAll(httpResponse.Body)